Depends on what dungeon it is and the group.

Trying to speed through AV will usually get you killed. Satasha, Tam-Tara, and Copperbell larger pulls are fine since everything dies so fast if your party is at capped ilevel. Toto-rak can be rushed through pretty quickly if you know the right path, Qarn isn't really efficient to speed through because of the enemy types and layout, Dzemael has that nice crystal buff that's perfect for pulling big. I could go on, but you get the idea.