Which classes to dual with?

Hi all,
I have 4 chars for dual boxing in 2 accounts. Druid Priest Rogue and Warlock. Which grouping would be easiest and fastest?
As far as i read priest warlock is a great combo but rogue druid is not so good. Any suggestions?

I guess a resto druid with a rogue would chew through stuff pritty quick. I rather enjoyed a bear tank tho with a priest healer you should be able to gather up loads of mobs and burn them down with maul and swipe ect. You will probably get the bug tho and want to increase your team to a five man. You could even instant pritty quick with a bear tank and priest healer.

I'd add in a Lock/Priest combo.

I recently did a shaman/lock, and nothing touched me at all.

even a SP would add a lot of DPS , and if you spec Demon, that lock's pet will hold a ton of aggro.

I love the idea that Mortem put forth, but I have never been able to box rogues for some reason.

Stephen