Got to 80 a while ago, but...
Got to 80 with my main and second teams a while ago, but I did recently get Champion of the Frozen Wastes on my Holy/Disc priest. Of course, that was NOT multiboxing. I do dailies and level toons and do old-world content multi boxing, but I strictly play one toon at a time in Northrend heroics and raids.
My guild loves that I always park my mage outside the raid instances for tables, portals, and buffs when we have no mage, and that she's a max JC/Alch so I can hook folks up or have her "run errands" like grabbing items from AH or guild bank during quiet moments in the raid.