Yes, but if you SW
and then get hit by a blue fireball, and perhaps wasn't at 100% hp, you die.
My point is that SW
is definitive NOT SAFE to use on the majority of Ulduar encounters,
especially not in progress raiding, where healers also have to learn the fight, and is unlikely to focus ever so much on you as ranged dps.
Shadow have a impressive survivability with Vampiric Embrace, and enough mana to keep up PW:S on ourselves for those fights where it's reasonable to do so (Razorscale is one).
I only healed Ignis, so can't talk about survivability there, but it's a very simple fights, so it don't surprise me.
But on a fight like Mimiron, I must say I never found a good time to use SW
, as it was very intensive damage on the entire raid, and our healers were busy enough learning to move from missiles, and laser beams.