Strength-Based Phantom Blade Advice

I have GM/play credit in PFS to start a character at level 7.66, and a boon that gives me +2 to an ability score on character creation. I've never played a gish-type character before, and I don't want to screw this up!

I have a Duskwalker boon that fits with the subjective theme I want (it's not totally optimal, but the +2 ability score boon helps a lot), and I plan on taking the alternate Duskwalker trait for wisdom to diplomacy and charisma.

I would like to build with more focus on spells rather than melee damage; it seems like the spiritualist's spell list leans toward more control and support than straight damage. However, being this is for PFS I want to be able to do respectable damage if needed as well.

Ability scores
Str 16 (18 w/ belt)
Dex 12
Con 14
Int 10
Wis 18 (20 w/ headband)
Cha 8

Feats
1. Spell Focus Necromancy
3. Gr. Spell Focus Necromancy
3. (Bonus): Heavy Armor Proficiency
5. Combat Casting
7. Lunge

Traits
Ease of Faith (get diplomacy as class skill)
?

Spells
0: Virtue
0: other standard cantrips
1: Burst of Adrenaline
1: Burst of Insight
1: Chill Touch
1: Inflict Light
2: Boneshaker
2: Touch of Idiocy
2: Jealous Rage (seeems like a hilarious combo with Virtue)
3: Bestow Curse
3: Sands of Time

Stats
Melee: Phantom Blade +12 1d8+6 (-2 for spell combats)
F:9 R:5 W:12
AC 24

Other
Going to grab an ioun stone for proficiency with the falcata, though I enjoy the idea of switching up weapons too.

Questions
How necessary is Power attack? It seems like a good option since I can target touch AC, but perhaps something that can wait until later when the spiritualist has a larger pool. However, it's probably useful for fighting mooks and I will probably take it as the level 8 bonus feat.

Any missed opportunities here, or something glaringly under-optimized? Thanks!

No lunge till 8th level. Power attack or Spell Pen.

Questions

How necessary is Power attack? It seems like a good option since I can target touch AC, but perhaps something that can wait until later when the spiritualist has a larger pool. However, it's probably useful for fighting mooks and I will probably take it as the level 8 bonus feat.

First, you cannot target touch AC and use Power Attack and similar feats at the same time(firearms have an exception for deadly aim).

...

The bonus damage does not apply to touch attacks or effects that do not deal hit point damage.

The bonus combat feats for Phantom Blade count your Spiritualist level as your BAB and as Fighter levels for prereqs. Improved Critical is a nice fit for the level 8 bonus feat. Especially with a high crit range weapon. I also like Stricken Heart for Phantom Blade, since it shuts down a full attack on hit and for a full minute on crit. Not as much damage as Frigid Touch, but less common damage type. Your spellstrike crits don't use your weapon's crit multiplier, they are always x2. So I would recommend a rapier/cutlass/something else 18-20 over a 19-20/x3.

Wow. I have… never noticed that line in Power attack in YEARS of playing! Easily takes care of that question.

I'd like to avoid the standard rapier/scimitar setup if possible, hence the falcata (plus, style). Cutlass looks better for sure, though. I think you're on the money with Imp. Critical.

Definitely going possession once I get those 4th level spells; it's the icing on the necromancy cake. Thank you!

For weapon, I recommend an investment on Exotic Weapon Proficiency (estoc).

It can be wielded in two hands for Power Attack bursts, or in one hand for spell combat.

I'd spend a feat in proficiency at 3rd level and push back on spell focus.

I don't think you need improved critical as you can cast that through spells.

I am playing a Phantom Blade in Hell's Vengeance and my damage felt low compared to the rest of the party (and we had an illusionist and a bleeder)... but I was fairly self-sufficient. Some light heals, spell combat with the shield spell until I bought a decent buckler. I also went with spells like Purge Spirit to play up the Charon angle of the character. Now at higher levels, Imp Crit/Crit Focus/Staggering Critical while possessing one of the enemies and still manifesting my Phantom Cutlass feels pretty good. Oh they have a cave troll? Yeah, mine now. Revenant Armor pairs well with Possession, though with possession you body only appears dead so its unclear what actually changes with your body (like, does your body still need to breathe?)

If I went back and restarted the character I think I would drop the Charon deific stuff and probably try to fit in Disarming Strike or Tripping Strike since they stack with Staggering Critical and focus more on status effects on enemies.
Which ever weapon you end up choosing... the ioun stone for exotic proficiency is only 1500 gp since you are proficient in all martial weapons. You should be able to afford this easily as a GM credit baby. The 10k version gets you weapon focus for free when slotted into a wayfinder so basically no need to ever take exotic weapon proficiency.

I’ve done a similar character in the past.

I think there is something to be said for using the fighter feats to pick up the crit feat line. Since crit fishing is your best damage option as a 1 handed fighter anyway and synergises wonderfully with spell strike.

I agree with others who commented striken heart and vampiric touch, especially since you’re wanting to be in the front line but with only D8s.

Also heroism is a good spell for you, you don’t get many accuracy boosters and you won’t always be able to burn the points to hit touch.

Finally I would say I’m not convinced by bestow curse, your DC probably isn’t going to be staggering and I think it’s more of an NPC Spell to begin with.

Yeah, agreed: Vampiric Touch is way better then Bestow Curse as it has utility in addition to damage. Heroism is definitely on the list, but a bit later.

The estoc is an excellent suggestion too, as I has already budgeted for the Ioun stone.

Also aside from smart spells (especially overland flight) I feel like vampiric shadow shield would be an incredibly fun option if you got to that level.

Eh, Estoc is budgeted a little toward being a dex weapon. It has no other features useful over other exotics besides the minimum damage being a little higher (2d4 vs d8). Also piercing only.
Katana would be slashing 1d8 with the deadly property.
Rhoka Sword is basically a Katana without Deadly.
Spiral Rapier is basically a piercing d6 (ie rapier) with Blocking and Disarm features though you can't 2h it.
Urumi is another d8 slashing, but has the Distracting feature and that it can be worn like a belt. Since a Phantom Blade can effectively sheathe the weapon in their mind, that is less useful though interesting.
Wakizashi is possibly an upgrade over the Katana because its P or S, though it drops down to a d6. Still keeps deadly, though its a light weapon so no 2h option.
Waveblade is similar at d6 P or S and bonus vs being disarmed instead of deadly. Being disarmed isn't a big deal after 9 since you can just spend a point of pool and teleport it back to your hand as a swift.

Since Phantom Blades can't easily swap out weapons against damage type DRs, I would actually lean toward Wakizashi. So you have the choice of Piercing, Slashing or sheathing your Phantom Blade and dealing Bludgeoning with your unarmed strike. Yes, Reshape/Quick Reshape is a thing... but then anything keyed to a specific weapon type turns off (weapon focus, improved crit, etc).