I've experience it too lol to a point where i was cringing my face at how bad i looked for an i90 whm to the other players XD.
I was like qq i'm tryinggggg D:
But it got worse after the tank's emnity combos and damage mitigation skills failed to work when the tank needed them.
So his hp was dropping so fast and mobs were everywhere and were attacking everyone lol!
So i had to hope for the best and spam medica, cure 3 and medica 2 just cuz i couldn't afford to have anymore interuptions during my casts for individual targets.
We made it thru but not without a lot of pain and suffering
It was also so bad that during zone transitions (i.e the blue dotted line ), i was able to run past the line wait there a few secs and run back without switching zones. I just hit an invisible wall lol.