Yes druid + mage is a good combo its the first dual boxing set up I made. I started with them both just pretty much owning ranged but I am starting to experiment with the druid tanking while the mage nukes and this seems very viable as well. I know feral is traditionaly considered the best way to level a druid and I think switching from a balance play style to feral seemed to be much better dps on the druids part, I will have to test some more though to see whats best.

If you want your druid always to be the one your controlling you can simply bind certain spells with a macro

/assist druidname
/cast fireball

or just have a simple key bind

/assist druidname

and then proceed to do whatever such as sheep while your druid can switch back to dpsing or healing. The only problem with this is that your druid will momentarily have to stop dpsing or healing while you target another mob for your mage to assist polymorph. Does anyone know a more efficient way to target on a secondary character without the main manually targeting it?