We know that the pure tax is a reality. We know that classes with only a single DPS spec are catered too in every situation (because they need to be), so are therefor good at ST, cleave, aoe, etc etc.
Mages have been lumped with 3 very "meh" specs that we constantly have to farm AP for, farm legendaries for, that can change over-night because Blizzard get mad that one spec is being favoured over the other two, so in terms of "balance" they need to make sure all specs are mediocre.
I put it forward that it's time to do away with Frost, Fire and Arcane and just become actual Mages again, with spells from all schools, and one single balanced spec that is only as good as the players skill level allows.