spark says in his guide that gosac with high item lvl/highe haste is good with (trinket). and serv with lower item. but looking at icyveins guide they say sacrifice is always the better choice at singeltarget with trinket.?
Personally I only run Sac on Council, and nowhere else. I'm not sure about what kind of gear/stats you would need to want to use it on other fights, too, and I haven't really seen any data to that end either.
I use Demo/Sac on Council, Megaera, Twins, and Dark Animus. I use a pet on Durumu, Iron Qon, and Lei Shen. The other fights, I do as Affliction.
Sac/Sup/Serv sim at 207k/211.3k/212.8k for me, single-target. So pure singletarget, even with a 540 ilvl, Sac's not better (at simulationcraft, anyways). If there are more things to Doom, Sac will pull ahead, and if there's burst AoE to be done, Felstorms are good.