If the NPC is supposed to be a thread to players than doing them on one damage source alone is a problem in itself.
It's only a problem because there is currently a talent which makes the player damn near immune to physical damage.
The enemies aren't supposed to be a mirror image of the players. If they were, the game would be even MORE horribly broken. Imagine running into a group of enemies - they all take their turn first because they had higher initiative. They nullify your resistances, cast oil, cast fire, and then create a wall of ice preventing you from running out of the fire. Then they drop a boulder down, exploding the fire and knocking you all down. Their 2-hander warrior charges in, knocking down anyone still standing, and then bully-crits your squishiest character for 170% their max HP. You can't teleport out because you're knocked down, and even if you could you're still on fire and poisoned and slowed and their entire team is waiting to fuck you up.
Strategies like that are fun to pull off as a player, but not fun to have used against you. Enemies aren't supposed to have all the tools of the player, because it wouldn't be balanced or fun.
