I think this would greatly benefit the game in both a PVE and PVP sense.
For PVP, it would make people try harder and care more about the outcome in a random BG.
For PVE, it would make less people afk in LFR's and try to learn to improve on their class for dungeons and LFR.
When I say performance-based rewards, I'm not talking about being first on the DPS or heal charts, I'm talking about having a high uptime on abilities meaning you're actually playing the damn game and not AFKing, and having respectable numbers for that persons item level.
The rewards can be as simple as a higher drop rate of gear, gold rewarded at the end or a call to arms box rewarded at the end.
Thoughts?