Channeled spells consume the AM debuff as of the 2.2 release. There was a week or so on the PTR where it did not and that was ridiculous. As an example, I was pulling ~1100 dps on Boom instead of the mid-700 dps I get on live right now. The AM discussion in this thread ignores that period of time on the PTR, so that bug-fix has been taken into account.
I personally nuke arcane because we regularly have a spriest and get CoS but not CoE. I do chain-chug super mana pots (and love the time we spend in gruul's and TK) and use my
[Pendant of the Violet Eye] as well. In exchange, I'm competitive for the top spot in most fights and compare favorably to the good 10/48/3 mages I can find in WWS for Kara. I also get to keep ice block, which I love.