I've been messing around with the idea of a character concept that mixes aspects of the Rogue and Cleric. Typically, Rogue/Cleric is not the easiest multi-class combination to make practical. There is the Cloistered Cleric, but that mostly just gives extra skill points and isn't all that Rogue-like. And if one looks into 3rd party material, there is the Divine Agent, which is closer to the ballpark and splits the difference between Channel Energy and Sneak Attack, but isn't quite what I'm looking for either.
So I just created the Heretical Cleric archetype, which outright trades Channel Energy for full Sneak Attack and also has a few abilities that make it similar to a Magus, using Spell Combat instead of two-weapon fighting. I also am still working on some custom feats that can help out such a character.
Here's what I have so far: The Heretical Cleric
Feedback, suggestions, criticism, all welcome.
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Sorry, about that, the link should work now: The Heretical Cleric
I think what you are attempting is possible, but I also believe that it could be better suited as a prestige class. Forgive me for saying this, but the archetype you have written seems to have too much of an agenda in mind. I feel like you traded out features you didn't want in order to get your favorites (sneak attack and spell combat). This doesn't feel like a rogue/cleric mix. It feels more like an death cultist. And spell combat isn't part of the cleric or the rogue. There are weapon proficiencies that neither class has.
My suggestion is that you dial back sneak attack to a slower progression - maybe like the slayer's. This will give some room to add other feature to introduce other elements of the rogue. An archetype or class should be able to cater to multiple builds, and this one seems to cater one kind of build. An assassin priest, I want to say? Expand the skill list, add skill points, and add acceptable domains to allow for other rogue aspects such as trickery, social charm, cleverness, crime, etc.
I think what you are attempting is possible, but I also believe that it could be better suited as a prestige class. Forgive me for saying this, but the archetype you have written seems to have too much of an agenda in mind. I feel like you traded out features you didn't want in order to get your favorites (sneak attack and spell combat). This doesn't feel like a rogue/cleric mix. It feels more like an death cultist. And spell combat isn't part of the cleric or the rogue. There are weapon proficiencies that neither class has.
My suggestion is that you dial back sneak attack to a slower progression - maybe like the slayer's. This will give some room to add other feature to introduce other elements of the rogue. An archetype or class should be able to cater to multiple builds, and this one seems to cater one kind of build. An assassin priest, I want to say? Expand the skill list, add skill points, and add acceptable domains to allow for other rogue aspects such as trickery, social charm, cleverness, crime, etc.
In a way you're correct about the prestige class agenda. Before I came up with this idea I was coming up with a Divine Trickster prestige class that is close to Arcane Trickster. But it seemed like a lot of my ideas that were different than Arcane Trickster's abilities worked better as part of a Cleric archetype first.
The concept here is more like a Cleric that also has Sneak attack and mixes it with their spells and has and a few unusual magical abilities, than it is about being a skill monkey, but with a dash of the rogue's stealth, and possibly with the character starting with 1 level in Rogue for the skill points and Trapfinding.
But it seemed like in order to make the simultaneous casting and melee combat roles as functional as it could be, I needed to better mix spell casting and combat. Spell Combat seemed like a good solution because of the action economy it provides. That ended up pushing it towards feeling more like a Divine Magus with sneak attack than a Rogue. But in a way, I think of Spell Combat as supplementing the assumed two-weapon combat style of the Rogue.
I admittedly got a little power-gamey by adding weapons like Estoc and Elven Curve Blade. I suppose I was thinking ahead to possibilities that would make for a cool Spell Combat character. My thinking there certainly has nothing do with the Rogue. Keeping class skills per level at 2 is also a little feel bad for me too.
I did have some hesitance at first about giving the archetype full Sneak Attack, but I wanted it to really feel like a Rogue Gestalt in that one aspect. I could still play around with it, maybe keep it every two levels but delay it by one level, or make it every three levels.
The idea behind Dual Casting also seems like something that might be better or more generally applied to arcane casters, or as an option for Magus characters.
I was also originally vaguely thinking of giving it a ranged option but it didn't seem to fit once Spell Combat was there. Maybe it's possible for the 2nd level ability to function like the Ranger in giving you a choice between Spell Combat and some form of Ranged Spell Combat.
I agree with Ciaran Barnes that there seems to be an agenda here. It's like you had a specific character in mind and made an archetype to support that, rather than creating an archetype that can support many different characters and concepts. The flavor text is incredibly specific, and hedges out other similar concepts that might have different flavor in mind. In some ways it reminds me of the vivisectionist alchemist that traded away bombs for sneak attacks, but got banned from PFS due to having a bunch of evil flavor text and some useless side-dressing class features that were evil.
It's somewhat weird that you've removed access to typical Cleric domains and substituted your own. That very much restricts the options with the class, and leads to silliness like not being able to take the Trickery domain. This is especially notable since your domains are a fair bit stronger than the best standard domains, so it can't even be said to be for balance reasons.
The Stealthy Infliction class feature doesn't actually do anything. The inflict spells all call for melee touch attacks, meaning they're a form of attack and can already benefit from sneak attack. No ability is required to do this.
Spell Combat is a bit much. It's the signature ability of the magus, and giving it to another class with 9-level spellcasting (even if diminished) is being far too generous. At low levels it'd be kept in check by just how few spell slots you'll have, but eventually that 9-level progression will simply overtake the Magus in spite of that diminished casting. I'd say scrap this.
Dual Spell Combat is nasty, and can allow for some crazy burst damage with spells like Harm. It's a bit tricky to use since you need your weapon sheathed to do it, but it seems a bit too much in spite of that weakness.
The Blood domain is overpowered and abusable. The blood leech ability is significantly stronger than other comparable 1st level Cleric abilities, but Blood Lust is the real offender here. It has no daily limitations, so you can just keep on regaining temporary hit points over and over again throughout combat. It's also abusable out of combat since it's very easy to trigger by attacking a helpless low-CR opponent and has a long duration.
The Force Domain is problematic since its 1st level power is useless until higher levels. It effectively amounts to having no 1st level power at all and then getting two powers at the 6th level. This is just bad design. Conjure Force Weapon is too good for a passive ability, since that lets you get away without buying a magical weapon at all (freeing up wealth to be spent elsewhere). Put a daily limit on it and it's fine, though. Thematically the spell list seems to scream "elementalist" and not force expert. It's also at odds with the class, as most of the spells there cannot be used with sneak attacks.
For Subterfuge, the Shadowstep ability is ludicrously broken on high-level characters, which can get the chance of attacks to fail up to 50%. Even if its numbers were lower, a passive general-purpose effect like this is simply too good for a low-level trash ability. Shadow Strike is poorly phrased, and I'm not clear on the intent here. Is it allowing me to immediately make a free attack after casting dimension door against a target of my choosing, or do its benefit apply to the next attack I make normally after casting dimension door? If the latter, how long can I wait?
As for your feats:
Finesse Grip is a bit too strong for characters with the spell combat class feature, allowing them access to a one-handed finessable reach weapon. Aside from classes that absolutely need to stick with one-handed weapons, though, it compares rather equitably to the elven branched spear. Take that with a grain of salt, as many people regard the elven branched spear as overpowered.
Stealthy Spell is much too good. It's like Spell Perfection, except for low levels and it stacks with Spell Perfection. Quickened Dazing Empowered Intensified Fireballs as 5th level spell slots? Yeah, we're done here.
Thaumaturgic Specialization is too good. The Cleric spell list was never designed with specialization in mind, so some schools are almost completely barren and could be opposed trivially. Cherry-picking off the Wizard spell list is insanely good.
Threatening Touch is one I'd keep an eye on, but just at first glance it doesn't seem broken. However, the low prerequisite barrier combined with how many classes can potentially make use of it make me weary that there's a potentially broken combo here. Definitely a very powerful feat no matter how you slice it.
But it seemed like in order to make the simultaneous casting and melee combat roles as functional as it could be, I needed to better mix spell casting and combat. Spell Combat seemed like a good solution because of the action economy it provides. That ended up pushing it towards feeling more like a Divine Magus with sneak attack than a Rogue. But in a way, I think of Spell Combat as supplementing the assumed two-weapon combat style of the Rogue.
Not being able to both cast and fight at the same time is precisely the limitation that keeps Clerics from being completely bonkers. They're already one of the most powerful classes in the game precisely due to their ability to do both exceptionally well. I would suggest using the Warpriest as your starting point rather than Cleric if you want a divine magus with sneak attacks. Having a 9-level spell list on top of all the other abilities you're talking about is excessive, but with a 6-level progression it might be more doable.
It's somewhat weird that you've removed access to typical Cleric domains and substituted your own. That very much restricts the options with the class, and leads to silliness like not being able to take the Trickery domain. This is especially notable since your domains are a fair bit stronger than the best standard domains, so it can't even be said to be for balance reasons.
You're right that they are stronger than typical Cleric domains. I think this was purposeful because I felt like I had to compensate for something. I definitely can see why many of them look overpowered. I think the reason I took away access to normal Cleric domains is because I wanted the class to feel like it had access to magic that normal Clerics don't, as part of the magical aspect of the class. It's slightly tempting to want to approach the class as having an aspect of Thaumaturgy.
The Stealthy Infliction class feature doesn't actually do anything. The inflict spells all call for melee touch attacks, meaning they're a form of attack and can already benefit from sneak attack. No ability is required to do this.
As far as I'm aware, the difference is that Inflict spells do not actually make a touch attack roll is part of the spell, unlike say Vampiric Touch, so sneak attack doesn't apply to them. Am I wrong about that? I wasn't 100% sure but if that's the case, then yea, it is a useless class feature.
Finesse Grip is a bit too strong for characters with the spell combat class feature, allowing them access to a one-handed finessable reach weapon. Aside from classes that absolutely need to stick with one-handed weapons, though, it compares rather equitably to the elven branched spear. Take that with a grain of salt, as many people regard the elven branched spear as overpowered.
Finesse Grip, in basic form, is just my attempt to bring back the Monkey Grip feat from 3.5. D&D. It does have more power than Monkey Grip here though, due to the Special text, and that probably drives it over the top.
Threatening Touch is one I'd keep an eye on, but just at first glance it doesn't seem broken. However, the low prerequisite barrier combined with how many classes can potentially make use of it make me weary that there's a potentially broken combo here. Definitely a very powerful feat no matter how you slice it.
I would definitely consider raising the prerequisite barrier.
I think you should move back towards your divine trickster concept, with less of the divine magus concept. If you are feeling ambitious, try making something that could have some of both depending on the player's build choices.