Ghost Crawler has stated several times that the classes are not meant to be balanced. He has also stated X class is meeting their target DPS.
Putting the two together it is reasonable to assume they have target dps for each class and they have decided in at least a rough way the order the classes will fall on the dps charts.
He also stated that having all classes do the same dps would not be fun and I don't know where he gets this. It is not coming from most players. Skill should determine the dps breakdown not GC and team. What is not fun is playing a Shadow Priest and knowing you are not going to beat half the classes giving equal skill.
If that is the way they think it should be, the least they could do is give their class target goals so players can make an informed decision when selecting a class. We already know mages and warlocks are at or near the top.