Casters want melee mobility reduced in PvP so that they can turret down melee. Melee want caster mobility in PvP reduced so they can avoid being kited. Ranged want cast on the move mechanics to remain in PvE because without them, they have to stop casting when fights force movement. Melee want those mechanics gone because they're part of why ranged are brought to raids over melee - melee can't DPS on the move nearly as effectively, between having to stay in range of bosses and having a positional requirement ranged don't have. If the boss drops fire on himself, the ranged don't care, but the melee have to either stop DPS or die.
We know some or all of these things are going to be addressed in Warlords. The perennial fight between ranged and melee in PvP (ranged want to stay the heck out of melee range, melee desperately need to get into that range) and the constant tug of war that is raiding (where balancing between ranged and melee tends to always favor ramged - most raids bring twice as many ranged players if at all possible) will be affected by the expansion's sweeping changes. To quote CM Lore's twitter feed:
PSA: There are a lot of interconnected changes happening in Warlords. Item squish, health rebalancing, spell scaling, CC disarmament, etc.- Lore (@CM_Lore) February 12, 2014