There's several things that killed wpvp. Dishonorable kills is not really one of them.
- Queues for everything you want to do. You hardly ever have to move out into the real world. In vanilla I knew where every instance was located because you actually had to move there to do the instance. Now I don't even know where 99% of the instances is actually located. You just queue up for it with one mouseclick.
- Flying mounts to avoid conflict while leveling and questing.
- Guards that stun/dismount/web/stun/stun/stun/silence/stun in cities and quest hubs.
- The addition of PvP gear which excluded the PvE'ers from any meaningful PvP.
Just face it, world PvP is something you often engage in because you are forced due to the circumstances/situation. These situations occur less and less because of the reasons above. Players will only very rarely go out and search for those situations, you have to force the players into those situations.