Longstop is one of those dungeons where smart play is better than just aoeing. Meaning yes you need to get out of red zones of nastiness yes you will need to pop cd yes your mages/healers should sleep mobs. Using your stun is also helpful in saving your butt. It doesn't get any easier from there. Try doing stone Virgil without a cc. The healer I head in duty finder for the life of her couldn't sleep a target and heal me without a 10sec gap.

Tldr: Use cc, use cds and win