Guardian is going to be your best bet for that thanks to Guardian Leap: the other tanks only really have Guard to keep their healer alive; Guardians can Guardian Leap to throw a nice big survivability buff on their heal buddy (not to mention that it can bounce them over to their heal buddy immediately if they're pulled out of Guard range or whatever), not to mention the slows, pushes, stuns, etc. that they get. You're not going to do terribly impressive damage as a Guardian in PvP, but you can play interceptor and defense quite well.
For some reason I can't play Healer class. Tried it and it just doesn't work for me, so I would like to make a tank.
Lately I've seen a surprisingly low number of healers in WZs. There are a lot of healer classes, but in 7 out of 10 WZs (according to scoreboard) there are no healers that heal. I am a watchman and I regularly see myself and my measly healing at the top of healing numbers. Rarely do I see one or maybe two (can't remember the last time this happened) that excel at healing. There are usually several of us with low healing numbers but so, so few real healers.
I try to protect them when we have them, but I can only protect them by focusing on their attackers. That is not enough. There has to be a tank with some sort of guard on a healer.
So I thought that maybe the lack of protection is the reason many healers do not heal in WZs or even go there. I would like to try tanking WZs with the sole purpose of protecting this so much needed class in every WZ. Maybe that could make a slight difference.