I think it does. Its only an issue late game, and there is no gain from stacking more and more damage spells. Get fire magic, focus on crit chance, get all that reduced and free cooldowns plus rift mage mana gains, and just spam the crap out of rift magic. Its all the damage spells nessesary.
Perhaps. People talk about stacking more and more damage spells like its the only other thing to fill your slots with - as I said to the other guy, you're not doing this in most cases. You're having to chuck out out teleports, crowd controls, shields etc to support dispel, not, as some say, '15 other nukes'.
Rift Mage is perhaps the best suited to using it though, as the spec 1) has the fastest overall cool downs, and hence can reuse spells much more efficiently and 2) isn't significantly better than a normal mage at handling barriers. For something like a KE, that realistically has no need for any other anti-barrier spell, it's not clear cut.