Tanking in PvP is fun but it is not rewarding if you are not in a group. Let's give you an example. If you play solo and you tank 10 players and during that time your alliance kill them you won't earn a big amount of AP. It doesn't matter that you absorbed almost all the damage. Now if you play solo and you heal your alliance members who killed these 10 players then you will get a nice amount of AP.
I can think of two videos I've seen where Shaliza was killed.The greatest build in pvp happens to be a tank, but not a typical tank as you might think of. Everyone in PVP knew who she is. She is Sheliza of EP (NA), they call her, "Unkillable". All the best players or dps builds you can see in youtube, can never take her down, it will always be a draw or win for Sheliza. She is the only one who can run the entirety of Cyrodiil afraid of noone.