WINTERGRASP / TOL BARAD

So i would like to report a some kind of exploit in this world pvp zones. for the moment it doesn't happen much on Tol Barad but mostly on Wintergrasp. You can just leave and join zone with no problem. I am about to kill someone he just disappears and in few sec he is back on full health. I mean you really got to be stupid to allow players to leave while in combat and than also give them the ability to join back right away.

Can someone actually put a COOL DOWN on that thing????