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Other domains give damage types that are not commonly resisted. Stat blocks list fire, cold, and other resistances separately from the "bludgeoning, piercing, and slashing damage from nonmagical weapons/attacks" that many powerful creatures have. That caveat is also never used for non-weapon types of damage (b/p/s), to my knowledge.
This means that even with a mundane weapon, a cleric with divine strike usually has a way to deal consistent, unresisted damage. They deal a different damage type, that might not be resisted. But war clerics deal the same damage as their weapon attack, and that should make it bludgeoning, piercing, or slashing from a nonmagical weapon.
Now, the flavor text says " you gain the ability to infuse your weapon strikes with divine energy." But unlike, say, monk's ki-empowered strikes, it never says "[this attack] counts as magical for the purpose of overcoming resistance and immunity to nonmagical attacks and damage" under divine strike, so it should still count as mundane damage.
That makes it sound like war clerics' divine strike ends up being a little rough compared to some of the others (though trickery domain probably has it worse). Have I interpreted this correctly?