Apparently NPC invokers have enough intelligence to attempt to try to avoid casting against resists and aim for vulns. (IE: Not casting icicle against felars or lightning against storm giants, etc). Unfortunately, they don't recognize Mantle of the Phoenix as a traditional resistance. Therefore these NPCs will try to fireball, wall of fire, and nova Marans - happily healing them as they try to kill them.

This seems to be most noticeable with felar being vuln_fire and storm giants resisting most other damage.

Should be reproduceable with any all-path invoker NPC facing someone with minimal resists (lightning, cold seem to do it pretty quick) and mantle of the phoenix.

They'll be more wily now.