Looking for some input.

I have my main account with a couple geared 85s currently (paladin, priest, druid, dk). I was planning on doing RaF with three accounts, A - B - C and boosting a few more characters. It sounds like the best way is to boost some using A, the use a new toon (now 80) on C to boost A & B to 40, then grant levels. My question is what is going to be the easiest toon to boost to 40 with?

My current thought is to (hopefully) do a couple sets. The toons I can see boosting are:
warrior, hunter, rogue, shaman, mage, warlock

Eventually (depending on how this goes) I might try to have one of each at 80, and probably a set of three of either shamans, mages, or maybe DK's.

So my initial question would be, out of the list of six classes above, which would you recommend using at 80 to boost some toons to 40?

Thanks.