There's the blood kineticist archetype.Mesmerist would synergize well with the will saves required for most necromancy spells and gets some good ones.
A holy vindicator makes themselves bleed.
And a reminder about fervor, only buffs can be swift casted, as you can only target yourself with them.
Oh, and arsenal chaplain is an amazing archetype for WP.
A friend of mine plays a blood kineticist. Very interesting concept but does not incorporate much of the spells/melee attacks I'm looking for in the build.
Mesmerist is definitely an interesting idea and seems like it would sync up well with an Eldritch Scion Magus. The painful stare would bump damage and hypnotic stare would weaken enemy will saves as you said. The spell list is decent but overlaps more with magus as opposed to getting some of the cool ones from cleric/warpriest necromancy list.
Holy vindicator is a very interesting prestige class! I definitely like the theme, the full BAB, and the d10. As a warpriest base, I wouldn't be able to start the prestige class until level 8. That combined with faith healing vs Dhampir negative energy affinity leaves me wondering if it might be better in a home game than PFS.
I've definitely seen Arsenal Chaplain mentioned a few times. Definitely no loss on sacred armor and to a lesser extent sacred weapon damage but I still need to familiarize myself with the blessings to see if it's worth being restricted to War only.
The Impaler you say, eh?
Great feat for the build! Although it looks like a pure warpriest couldn't take it until level 12 as a bonus feat due to the BAB +11 requirement. Would be a nice 'retirement' for the character though. :)
Thank you both for sharing your ideas! I wonder if there are additional suggestions out there.