Hey, long time reader here, finally came up with something to contribute.
Before 3.0.8, it was possible for a paladin to fly into the warbringer, bubble, and 1 shot him. However in the last patch he was buffed to a lvl 80 elite, and as such now has 121k HP.
It IS however still possible to kill him, and here is how:
(This probably requires a paladin, I did this as Ret spec, probably doable for holy and prot too)
1. Mount up in krasus landing and fly over into warbringer area as before.
2. Bubble up before you get ported, and hit him.
3. Now KITE HIM as far as you can, your aim is to get as close to the exit to the horde area as you can.
4. Your bubble will run out long before you can exit the area and you will get ported, however if you managed to get far enough, he will not drop aggro, and will run towards you at your ported location. Use some long range attack (New Hand of Reckoning is ace for this) to ensure he doesnt reset whilst running towards you.
5. Once he is out, you can now take him anywhere in the city. Amusingly, if you kite him to the alliance sector, he gets ported out + stunned (you can use this time to heal yourself if you get a bit low).
Hope some of you find this amusing, was something to do whilst bored before the patch, now there are lots more things to do with him ;D