I'll recommend IS Boxer.
It's $36 per year, as a subscription.
But really any of the software options is an enormous step up from clicking between windows.
Other options include: http://www.dual-boxing.com/showthread.php?t=24992

Most of us have multiple toons, rely on follow for the slave movement and have some form of assist.
The easiest is a Focus based approach, where the lead toon is everyone's focus, and everyone follows or casts at the target of the focus.
An FTL (Focus-free, Target-free, Leader-independent) system is harder to set up, but preferred especially for PvP play.

Depending on your goals in wow, particularly PvE, PvP or Both, some classes are generally better then others.
But if a given combination is fun, then go with that, as fun should be the deciding factor in what you play.