My idea is you will be casting every 1.5-2.5 sec on your mage, but others will just be most auto-attacking. That is tricky on my part since I am used to just mashing my attack macro about 2-3 times total. For the slow spell, it isn't going to be until lvl 51. That is a LONG time until then. Use whatever you think will help until you get there then you can respec if you want to get it. My 2cents. You have locks for anti-runners, so slowing mobs with ice isn't that important. You probably don't want your mage to get aggro so Blizzarding is probably out. I might chose arcane for arcane missles since it is channeled and it will auto-follow mobs incase they move around. Nothing like a "you aren't in facing the mob" to piss you off.