PvP Quick Class IDing mod
 

One thing that has been affecting my performance in battlegrounds is that I can't quickly tell the classes of my enemies based on their looks.

Examining the enemy frames help, but for a group of enemies I need to click on each one or wait for them to attack. Obviously the latter is not preferred.

So I ask you what UI can help me quickly ID my opponents so that I know who to pick my fights with.

I would suggest looking at their tooltip. There is no range limit for this, as there is for nameplates. You can have the tooltip anchored to your mouse, if you prefer, and/or you can have it colored by class, etc.