Up till now, I've only ever raided on my main and I just run dungeons with my multibox team. As a a guild, we're clearing BWL in an hour, then also clearing MC & Ony weekly for chance at bindings and whatever odd piece of gear people still want. We're at the point where we get quite a few people who drop once we're down with BWL, so I'm trying to talk my guild into letting me multibox MC just to fill out the raid.
If they let me, I'd bring up to 4 mages and 1 priest. My "main" is 1 of the mages and I'd even have the priest (disc/holy) generally performing as really bad mage - just smiting away at whatever my main is frostbolting. I could have the priest help buff & decurse, but I don't think I'd actually want to try healing at all - perhaps just a bit within my own party.
I can imagine Rag will be a bit of a PITA, I'll have to stack together and try to get through it with GFPP and some fire resist gear to avoid getting blown into the lava. The bomb on Baron should be easy enough to manage even if I'm targeted (5 accounts on 3 monitors so its not too hard to just mouse over and control from another screen where needed.)
Are there any other mechanics that are challenging to multibox through? Other advice?