Broken enemy modifiers

Some enemies shouldn't be able to have certain modifiers, because it makes them impossible to deal with.
I've had this happen multiple times, and every time, it's resulted in an unpreventable death.
I've had the Chimera in Trials of Chaos with Regenerating, so it was literally un-killable, because I would get it to phase, then it's back at full, just in a different location.

Then while mapping today, I ran into a Wraith with Mana Drain. Note, they don't appear until they're right on top of you, so there was no way to preemptively hit it or know it was there. Then the Wraiths can teleport to stay on top of you, keeping you at 0 Mana, making them impossible to kill solo.