I've been using mods to fix the class. I agree that they should get extra attack, and spendable charges at least on par with bards to boost allies and self hit chance. Leveling progression can be similar to bard for balance when multiclassing. That model has already proven as tried and decent, after all. These changes are enough to produce a functional subclass.
Multiclassing it would be suboptimal, but that also means all features to function *need* to be included in the class progression. Since it's a full spellcaster, even extra attack at level 6 or 7 would be fair. The war priest charges would be better off replaced with a bless on demand style of function to improve hit chance after having rolled the dice. You'll want a balance between how powerful the boost is and how often it can be used per day. It should at minimum end up equally powerful to alternative classes.
