Well...you could increase DF CD, doing nothing to comps like FMP and RMP, cause you use DF a lot of times for CC anyway and can still get of the "trololo u died in a DF"-scenario. Sure, you'd have a higher chance of having a def cd ready, personally, I could accept a change like that.
Someone mentioned mage being reverted to a cc-supporter with little add-up dmg, I would have nothing against that, but good luck convincing blizzard to have a totally useless class in pve, cuz its all about da damagez.
You could reduce the cc mages provide. Lets see. Most of Melees are pretty biased when arguing about mages, because they are sick 'n tired of standing in novas 24/7, like it was in cata, and a little better in previous expansions. Novas were cut to 2 once every 25 seconds, but dispell-cd was implented, so I guess its about the same as it once was or better as in cata. (I miss CoC root a little, but novae are still reliable so.)
As mentioned in my first post, I think PoM Frostmages are retarded, as are DF Firemages. People complained about instant RoF (even nerfed) in cata, so why not get rid of it completely. It should be okay with a 1,5 sec cast, so its still somewhat useable in rBGs, and good enough to peel your heal against double/melee or to root hunter-zoo.
20 Second Counterspell inline could be changed, we could make blanket cs on a 30 second cooldown and reduce it to 24 seconds when used to kick a cast. Same could be used for warlocks.
I think orb really isnt that great, it ticks a little high with cds, personally, I'd prefer the old cata one, doing poor dmg on its own, but proccing FFB, impact (now gone, but thats alright) and FoF like mad
Maybe putting FFB Proccs back on snare-effects/frostbolt, rather than proccing it from bombs. (NT TO THE GROUND PLEASE)
I understand that Holypalas and warriors are ubar mad to get globaled in a DF, every time I see a warrior, ret or holy in arena, I know chances are really high to win the game. This should be changed. But I can't recall a MMO being in a good balance, there always will be classes which dominate others, everyone saw what happens if you make warriors "balanced" against frostmages, 5.0 times...