Personally I love a mage/priest combo, especially when aoe farming. This was my combination for my first dual-boxing experience, I have since advanced to 5-boxing. If you ever decide to upgrade to more accountsthe mage works well for boosting your own characters. Although mage wasn't on your list of things you wanted to level. I find the healer/dps combo to be very effective and also gives you a bit of versatility for when you decide to group with others

From my experience and using your list I'd say try:

Priest/Warlock or druid /warrior (druid healing spec)

or you could aways do some shammys liek most other people