Arcane Missiles

[Dreez]

The push back portion is true, what i mean though is for example, rain of fire, if you get out of it, you cancelled the cast yet still paid all of the mana for it. You can of course stay and finish the cast, but then you'd end up taking a lot of damage by being in the rain of fire.

This is true, it is certainly a drawback. The DPS loss would be less because you might get a tick or two off before you have to move while expending the full mana cost.

As a sidenote, does each tick of Arcane Missiles have a chance to proc Clearcasting? I do believe this is the case, but I suppose it would be good to verify this!

No, there's only a chance on debuff application (only once when you start channeling)

[Vaped]

So i've been messing around with arcane missiles for a while and i like leveling up with it, just because i've done frost and fire leveling and i'm quite bored with it. Yeah it does aggro mobs as soon as you cast it on them, but throwing a Fbolt at the target then casting AM solves that issue, and at my current level getting frostbite to proc before i channel is amazing. the reason i love Imp AM is that i don't have to worry about push back. It's different leveling that's for sure. Probably not viable at 60 in raids (PvP maybe!) i haven't gotten to test it that far, but if you're leveling to 60 again, i'd suggest theorycrafting with things that aren't popular, it's a way to make the leveling process so much more enjoyable. (Next thing i want to try is leveling up is a rogue with 3/3 set up, or a warrior and stacking crit over AP; it brings something new and interesting to the game that i have yet to experience!)

[Stalk]

No, there's only a chance on debuff application (only once when you start channeling)

This is a bug then. Arcane Missiles has always worked in this way that there would be a 10% chance to proc Clearcasting for each missile that lands. This talent was the sole reason why you would see mages spamming Arcane Missiles in old raid videos. The 10% chance to proc Clearcasting only at the beginning of the Arcane Missiles cast was a Wrath of the Lich King change in Patch 3.0.8.

Arcane Missiles should also not aggro mobs before the first instance of damage hits them a.k.a. "it aggroes mobs as soon as you start channeling due to invisible debuff". Also, it should not be cancelled when other buffs push it off of the stack (if this still happens) just as all the other channeled debuffs should not auto-cancel channeling of the spell when the debuff is pushed off.

[Dreez]

if that's the case and you got proof of it, report it on the bugtracker^^