3.2 making invis not suck anymore will be amazing for this. Nothing sucks more than hitting it, then RIGHT before you fade out getting hit, which ruins it and wastes the long CD.
As for 2 mobs at once, just poly one on the pull, toss slow on the other, PoM ABlast -> ABlast -> ABar = dead 99% of the time. Then just wipe up the other one. I love Mage for soloing. I personally could NEVER drop Frost (run, grab 10 mobs, Nova, Blink, Blizz, Profit) but it is nice to change things up.