4 60+ Characters, only three accounts with BC, how should I arrange this group!

I have my main my priest (acc1), a level 69 lock (acc2), two level 60 boomkins(acc1 and acc3), and a level 55 shaman....(acc2). Also there is a mage that I levelled with the shaman but I dont like him enough to make him a levelling priority.

So now I have to make a sophies choice about the ultimate way to end up with my toons arranged. I'll never be able to play more thn three of them at a time, so which of these sets never need to be on at the same time?

Boomkin and priest? (this would entail moving my lock to account3)

What would you do? I feel like this decision should be made now so that the right boomkin for the set gets levelled and I dont have to shuffle later. And having the shaman (#1 levelling priority) on the same account as my more powerful babysitter seems counterintuitive.

Also the warlock has herbalism, which is worth no small sum of money, and I would prefer to use the lock to bring up the other babies, so my only real options at this point are to move my lock to account 1 with the priest, or 3... or my shaman to account 1 or 3.

you sure you cant just make acct # 4?