This deals more with the nature of dps.
As a general rule of thumb, arcane's dps and DPSE will always decrease as a fight gets shorter. For example for me to parse on a fight like H domo, not only do I have to be doing 50k+ dps, but I need everyone in my raid group to doing 45k+ dps, so that we can push him down fast enough that I will only get three burn phases.
Also your group's comp will force you to AoE more then it will let you single target dps, this will most likely hurt your over all dps unless you get in a really clutch burn. But remember good arcane dps is a group effort, I can't pull 50k+ dps on H domo unless my whole raiding group is pushing 45k+ also.