It's happened to me but I reroll before I level off them, 3 trapdoors makes them scary.

Oh we've all been gigabeed and Slugslid

Noone gets prof for killing 6 levels of slug sliders or is even able to do it at 9 wave on hardcore with crap gear.

True.

It was probably the most frustrating thing I could have gone through. I even tried the method of knocking them all down to low HP and trying to kill them all in one shot... I killed the bottom row with my bottomsup ability but before i could get two attacks in, there were three more! Sad end to the story though... I was fortunate enough to have some kind individuals attempt to help me out but when I created a group to clear them, the dungeon reset on me! Sad day but I learned my lesson to create a group when I first log on to avoid such miserable outcomes from arising in the future :)

Ironically this used to be one of the coolest monsters. The spawned mobs were given insanely increased drops due to a bug. If you were able to tank multiple at a time all you needed to do was let the screen fill and kill all but 1 or 2. Collect the loot and let them respawn. Rinse repeat profit too bad that was fixed... it was alot of fun

The dungeon doesn't reset when you create a group, only when you leave a group.

then that was my problem, I created and left one.... my own mistake i presume haha.
also note: my gear is crap so i was given a bit more of an issue with them :P