Implement a system that allows for 2 v 2, 3 v 3 and 6 v 6 to compete in arena's and mini games with rankings and rewards that are as epic as what the higher tier raids offer.
Instead of Guilds, allow for players to create and sign up for teams that compete in the league itself. Attach statistics and rankings to the system, this only natural in competitive play.
Rewards
1. Tier gear within the ranks that are based on skill (Like WoW)
2. Mounts
3. New Combos for PVP(based on skill)
In order to make players compete and want to get better, it is obvious that you must attach a carrot to the end of a stick in order for them to strive for it. Some people naturally are not competitive in nature, but do enjoy rewards for their efforts.
This idea should have been implemented 4 years ago, I am not even sure why it hasn't been now.