Prismatic Cloak was largely in an attempt to be able to maintain a little of the survivability of my current build, and the point in wands was there for those nasty times when I know I'll (cetainly with this spec) go oom with Evocation, mana gem and mana pot on cooldown. Oh, alright - it's because I needed one more point in Arcane for Spell Power, and I rarely use AM.
That said, if I were to use this build then I guess AM would have to feature in my rotation, so you may have a point... I'm just keen to avoid the cookie cutter build, so I'm trying to be a little creative.