agreed. specially BGs. throw a frost mage in the middle of a party, and it creates a massive disadvantage to whoever has less frost mages. frost nova / cone of cold / pet nova / shatter / deep freeze / ring of frost / ice lance spam + kiting slowed or frozen targets, etc. it's horrible to go on world pvp or bgs and get frost mages that knows enough to make a pain to the adversary.
this is a consequence of priorities. like blizzard keeps stating regarding lower levels, they are not interested in balancing at lower levels. same for bgs and all that, all that REALLY matters is top pvping. for bgs? both factions will have the chance to take mages, so no need to balance there. only for arenas, where dispel is used cleverly.