Would you like an in-game parser?

[Thunda_Cat_SMASH]

How could my group of 7 people kill sephirot 2 min faster than a 4 dps group? And we are in the same gear, I'm waiting for you to explain.

Familiarity with the content to the degree that you could probably do it in your sleep vs a group of players that don't know the content or haven't memorized every singleminutiae, causing deaths and lost dDPS by mistakes that add up over the course of the instance. Not sure! I can't think of any reason in particular.