Simply taking some time to familiarize yourself with combos/buffs and when makes the most sense to use them, and also to organize the hotbar in a way that is easiest makes a world of difference from my time in phase 3 and 4. Obviously many people know all this, but some I noticed did struggle with positioning. It is also important though for dps roles when looking for a smooth instance run to remember to let the tank establish hate before charging in and setting up their buffs and combos. I did find that in parties where enemy groups were numbered, things went more smoothly as well.