Yes, it's simply not doable for me. I've heard of a few people being able to do it, but I suspect they're burst specced Sentinels or some such thing, capable of burning things fast while using defensive cooldowns.
I am tank spec as well, and it's simply not possible without serious upgrades. I'm not even sure it's possible then.
the only people i know who have finished it had it bug and he died in one hit.