I commented on this earlier, but throwing it out there again: Archon is freaking amazing.
I'm burning through Nightmare Act 3. It throws a bunch of little dudes at you with a bunch of medium dudes, and you build up time-in-form on the little dudes and tear through the groups of medium dudes. My Archon morph is lasting longer than my armor spell, and I eventually let it go intentionally in order to re-buff.
Although if I do get caught out of Archon, it can hurt. It's painful trying to hack through hordes of little dudes with AP-limited Arcane Orb. Some Elites are better handled in normal form, too - especially if they're fast and tough such that you want Diamond Skin (this is also the one buff that doesn't carry over when you Archon morph

).
But wow. I can imagine the Wizard being an extremely fast Hell/Inferno farmer if this holds up. It's a consistent, sustainable 300% weapon damage to everything in front of you, plus extra tankiness on top of your armor spell. I can't wait to see if it synergizes with the passive that slows enemies that get hit with arcane damage.