although SPs.warlocks and other class combos make for better raid compositions in the "normal since", multiboxing demands simplicity as much as you can. Just like in 5 man heroics, where 5 shaman or 4 lack in CC..added buffs/debuffs. they more than make up in fire power and overall utility. Running 10 acnts with too many classes has got to be one big pain in the ass. So as few classes and you can get away with is best IMO.

We already know shaman make for super easy multibox friendly management. So the question is " would 6-8 shamans and two tanks ( any kind or combo of tanks ) work for most encounters. less buffs ? well tons of totems and every single totem would be down. way more dps than you will get out of mixed combos. In order to maximize a lock or mage dps, for example, you need to mash more than one button really. Not so with shamans.

So dealing with tanking two mobs at a time.. healing those two tanks and spot healing the raid AND dpsing= as few classes as possible, right?