Finding good synergy between classes is one of the difficulties of Multiboxing.

Some people mash keys, some of us carefully lay macros out.

Personally I think the *key* is castsequence macros.

This, in effect allows you to mash one button over and over allowing each character to cast their specific spells in sequence, once casting is completed on one spell, it moves onto the next, etc.

Keybinds themselves are rather a more "personal" thing. Go with whatever you feel most comfortable using.