sounds like a graphical glitch from time to time, functionally they still have the same HP so just hammer on em and they'll go down. its like when you see an ally with 0/100k health while they're really at 20k/20k.
Wrong. The 200k health mind traps exist/ We had a 200k health mind trap spawn in Nightmare EV 8 man two weeks ago. It took roughly 10 times as long to die as a normal mind trap. Only one spawned like that and I believe it was the second mind trap of phase 2.