Not sure why anyone would play immortal without 2/2 unstoppable. It makes all the difference especially in huttball. It provides immunity to everything, even knockdown.
I haven't lost a huttball(8 games, 5 of them solo queued without healer) since I respecced to this from rage.
If I play with a healer I never die and get 10-12 medals, if I don't play with a healer I die 20 times and get 10-12 medals still. I use dps gear and a shield generator in soresu form.
I just walk around taunting, slowing, chocking, stunning and occasionally killing people while continuously changing my guard target.
here's my spec, very similar to another spec that was posted here some time ago
http://www.torhead.com/skill-calc#101crGfzMbozZhRrzMZMM.1
I have to admit its a very boring spec to play, I don't think putting 31 points in immortal will change it. I've been pondering if I wanted to level up another tank for pvp but I am not sure if grapple/stealth will make pvp tanking more fun than intercede already does.