It's very possible while boxing indeed :)
http://www.pray3rs.com/screenshots/W...108_110520.jpg
For group setup the way we usually do it is:
Group 1
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2 tanks - preferably 1 pala 1 warrior/druid. We've done 2xwarrior, 2xdruid before as well, but pala + warrior or druid is the easiest.
2 healers - 1 priest, 1 shaman (have done priest+pala, pala+shaman and priest +druid as well, all seem equally effective) I do prefer having a priest here simply for the CoH which is really effective with a multiboxer, because when 1 shammy takes damage they usually all do (like the fire breathe at 3rd boss etc)
1 'random' dps, had a mage, lock, hunter, rogue, anything fits here
Group 2
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1 shadow priest (that feeds my shamans with mana)
4 ele shammies boxed
We've been doing this for over a month now, and the full group has bears. Started selling them now as well, 750g for each person in the raid every bearsale, easy cash :)
edit: with this setup we usually end up at 9 to 11 minutes left after the timed part. The gear of the healers and tanks (and shadowpriest) is mostly hyjal/bt, the random dps is often kara gearish as he is the random buyer most of the time. shammies are full full pvp gear (3s3, 2s4) with all the badge loot from the isle (chest, belt, legs, and boots from normal badges, also a lightning capacitor on each) they're all filled with haste bringing them (buffed/totems) to 1.2kish spelldmg, 39ish% crit and 230 haste