The point is that BW claims that all classes are within 5 % dps but if you look at how the average sorc/sage performs it's pretty obvious that this isnt the case. Hence, the must be comparing the top sorcs/sages to average players from other classes for it to add up.
I see. I'm always lowest DPS on our raids. I'm not the perfect player, but neither are the other 3 DPS, and 85% of the time I'm lowest. It's not like madness is a difficult rotation or my gear is bad either.