Do have the slightest idea how this encounter works? That you stack the buff on warlocks, mages, shadowpriests and tanks before anyone else because they blow any melee in terms of dps on this fight?
That would have been the dumbest reason i have ever heard to discriminate pet classes. I tell you why they did not include pets like they they did it with a lot of major buffs in almost every content: Either they are not aware that there are pet classes out there or they think its not worth the time to implement it. What do you think is more realistic?