Goning to chime in here and apologies if others have mentioned it before, I haven't read more than the first pages of replies...
After reading the Warpriest it does lack the uniqueness of the other class crossovers.
Its focus is very unclear. is it a fighter? a cleric? or even a Paladin?
What I think would help the warpriest is if you instead focused on the War aspect of the name.
I could imagine a warpriest tending to the wounded in battle, helping groups of people instead of just one, fighting alongside allies, bolstering them with blessings and divine power.
In essence I see a warpriest being more of a team player than a "look what I can do" one trip pony.
My mind flicks back to the Marshal from D&D and its use of abilities like , Battle Orders, Don't Die on Me!, and Stand your Ground, all of which would fit a warpriest IMHO and give the class a unique element beyond the fighter/cleric wannabe paladin stereotype its in now.
if your looking for ideas perhaps give them the share spell ability that casters have with familiars that functions on allies when casting spells from their spell list (1 per 5 levels),
Give them a unique spell list focused on the mass cure wounds with a tailored 6 level spell list, removing a lot of the cleric spells that focus on a single target.
Give them the ability enchant defences such as doors, walls, ballistas, and other war machines to help when the party must defend instead of going on the offence (perhaps conjure a few). I could see a warpriest blessing the water in a mote that repels undead or demons.
Give them a censer as a focus item maybe, or the ability to create and enchant then with spell effects.