As far as the rest of the group makeup, I'd urge you to really think about how you are going to tackle groups of mobs in heroics. A lot of people will just say "oh use leet pally tank you don't need CC". Most of those people don't appear to have any badge / heroic geared toons.

I have to provide the disclaimer that I have NOT multiboxed heroics yet, but I have tanked and healed dozens of them, so I know what it takes to handle the big pulls.

You should be aware that PVE multiboxers fall into 2 groups - non traditional burst dps (typically 5 shaman with some variation) or the trinity (tank / heal / dps|cc). Burst dps groups use non-traditional methods (kiting, elemental pet tanks, stoneclaw totems) inside isntances combined with insanse DPS to down mobs quickly. When you do a traditional group (as you are) you lose 2 spots to non-dps roles, so you're not going to just blow everything up (especially at first). For your tank to handle that with little CC you need to be well geared (to include some badge gear).

That's NOT to say you're proposed group can't handle it - I'm just suggesting you plan out how you will do it. For instance, you may need to use druid roots, spriest mind control, or warlock seduce in addition to your single mage sheep on big pulls. Read up on those forms of CC and think about how you would manage it with how you are controlling your toons and then decide if it's the right group make up (again, I think you can do it but some pulls will require some special prep). Several badges later you'll be able to just AE tank everything and kill it, but it can be a frustrating road getting there.