Not everytime you run a dungeon you'll get the same time.
It can be 10-15 minutes less even in the same gear, with the same dps.
WHM or SCH dps time gain is NOTHING compared not to get hit by a Tomberry Stalker or not to die from a Mountain Buster.
I never dps, and I always make good runs in few minutes, and when I have nothing to do, I do nothing, I just keep watching at the tank and maybe I Stoneskin someone te better protect everyone. I suggest not to dps, if you want to do it then dps the shit out of your cane, I don't care.
I'm out of this post
