3090 dps compared to 3000 is huge over a 10 minute (or even 25 minute) boss fight.

Fact is though, Blizzard said they wanted to make all dpsers equal (well that's how I interpret it), so mages shouldn't always out dps us. The other fact is, ele shammies are still (and have been for a long time in beta) lagging behind, so far behind they may as well bring a spare OT in case of emergency instead of the ele shammy, with no loss of raid dps.

2400 dps is what you should be hitting late BT, early sunwell. Not 10 lvls later. I guees we will see what happens when we are equipped in full t7 though. But I don't expect much until some changes are made.