That would make the class go from crap to pretty good. A class that attacks once per round doesn't work
To build a STR based caster, you want full plate because of bulwark. Otherwise, your reflex saves will be bad. You will want to do boosts to STR CON WIS CHA.
To go full plate, you have two options - sentinel or champion. Sentinel has the advantage of auto scaling proficiency (champion requires you to take a L14 feat diverse armor) and opens up mighty bulwark which gives +4 bonus to all reflex saves instead of +3 to only damage spells.
Best path for sentinel is human race to start with armor proficiency through versatile heritage or general feat. If you stay with dwarf, you would need to take armor proficiency at L3, sentinel at L4. If you go with this plan, start with
S16 D12 C12 I10 W10 CH18. Don't play an oracle without 18CHA. Problem with staying with dwarf is L4 feat cost could be used for diverse access. If you are human, you use sentinel as L2 feat.
It's much easier to build a DEX based caster than a STR caster. If you want to build a STR based caster, expect to give up on some role play options such as what race you start as.
I was disappointed with singular expertise for ways that encourage melee. Why should a drifter encouraged in using a gun in one hand and a melee weapon in the other have to endure a lower accuracy with the melee weapon? The class is so underpowered as it is, that singular expertise should remove the penalty to other weapons.
nonat made a video stating that paizo can't add potency to spellcasters because they added the shadow signet. If you look at a lot of creatures, their reflex dc trails their ac by a decent amount.
Fire giant ac 31; reflex dc 26
there are also lots of creatures that the shadow signet doesn't help you. However, this is nonat's reasoning of why paizo can't retro put potency runes for spell attacks.
Sentinel is not a must have for optimizers in all situations. It's a must have if you want to dump dex. If you keep raising dex, you can go from medium to light armor to save bulk and to enable light armor runes.
If you stop raising dex and stay with medium armor you are dumping reflex saves. It is this situation that sentinel enables you to dump dex without dumping reflex saves.
I played an orc primal sorcerer archetype champion in the slithering. I had battle medicine and was the only healer in the party. I used a greataxe.
I wasn't the highest damage dealer, but between healing and damage and some spells like fairy fire to outline invisible creatures, I was the most versatile in the party.
I played a fighter and a magus in different APs. The fighter did more damage, but the magus felt so much more durable in combat with spells like invisibility and stone skin.
I think it mostly comes down to expectations. Casters have versatility that martials don't have. For game balance, martials have to be able to do as much or more damage than casters.
Also, the game has many options. If you want to do damage, you can always play a martial.
I would change background to secular medic (dex/free attribute increase; battle medicine feat) to get battle medicine; increase medicine at level 2 with assurance medicine at level 1, continual recovery at level 2. This gives you auto success at battle medicine/treat wounds at level 2. I think battle medicine is fantastic at low levels where you need healing the most.
Other suggestion is first general feat at level 3 should be fleet to get 30' move. Speed is probably the best ability to buff; it also means your mobility works for 15' move instead of 10' at level 3.
Mobile shot stance is only poorly written if the developers felt that bow shots worked with a baked in manipulate action. If they didn't believe that's how it works, then it's not poorly written.
The side that believes manipulate actions are baked in can't accept that their interpretation might just be not what the game developers intended.
Inventor Archetype, are you trained proficiency in armor innovation? What about a martial weapon then?
How big a modifier is the gm going to give you? At first level, by the rules the dc to command a horse is 15; if you have +3 from trained nature with no wisdom modifier, you have to roll a 12 to command it successfully. It should be trivial imo, but by the rules it's not.
And if the gm says you auto succeed, then what's the purpose of the ride feat? The rules are broken imo.
From errata, skill checks can still affect map
Page 446: Attack Rolls. There was some confusion as to whether skill checks with the attack trait (such as Grapple or Trip) are also attack rolls at the same time. They are not. To make this clear, add this sentence to the beginning of the definition of attack roll "When you use a Strike action or make a spell attack, you attempt a check called an attack roll."
To clarify the different rules elements involved:
An attack is any check that has the attack trait. It applies and increases the multiple attack penalty.
An attack roll is one of the core types of checks in the game (along with saving throws, skill checks, and Perception checks). They are used for Strikes and spell attacks, and traditionally target Armor Class.
Some skill actions have the attack trait, specifically Athletics actions such as Grapple and Trip. You still make a skill check with these skills, not an attack roll.
The multiple attack penalty applies on those skill actions as well. As it says later on in the definition of attack roll "Striking multiple times in a turn has diminishing returns. The multiple attack penalty (detailed on page 446) applies to each attack after the first, whether those attacks are Strikes, special attacks like the Grapple action of the Athletics skill, or spell attack rolls." There is inaccurate language in the Multiple Attack Penalty section implying it applies only to attack rolls that will be receiving errata.
The point i was sort of making is that there is no fighter build that uses crossbows. Crossbows are far inferior to bows. All ranged fighters use some type of bow.
So if you are balancing guns with crossbows, there has to be a class option that makes using a weapon about the same power as a crossbow worth using. The current gunslinger doesn't have that class option. So the class as constituted with the guns offered sucks.
The biggest change in my opinion is tight math. In pf1e, it's very possible to do 1000% more damage than another character of the same level. In pf2e it's probably possible to do 30% more damage than another character of the same level.
This means that GMs don't have to plan for a wide variance of power possible in pf1e and every character will be somewhat useful. I have played in pf1e games where because of that variance in power, the weak characters are irrelevent.