Immortal is fine if you don't use the correct gear? Man, how come I didn't think of that logic?
Also, any spec can 'disrupt and support'. There's nothing special in the Immortal tree that makes them some god of annoyance.
More attacks are not affected by our mitigation than are. Any spec can go into Soresu Form and 'tank' a few people with a healer and their team behind them. The difference in damage taken is not huge, it is negligible and not worth the huge amount of output sacrificed.
I was a diehard tank for pve reasons up until about a week ago when I realized the spec was useless in pvp. My pvp set was nearly (champion) complete with 20k hp and somewhere between 500 and 600 expertise.
I am just as useful as a ball runner as Vengeance or Rage than I was Immortal, considering it is Force Charge and Intercede (and Guard for running with a carrier) that makes us great, not any of the worthless talents in the Immortal tree.