I've been raiding destro for a long time now. I know that dot uptime should be as near 100% as possible. What is considered a good amount of uptime for immolate?
Get better at pre casting (casting immolate .1 +casttime before the dot wears ) and you'll see your uptime get closer and closer to 100%. DO NOT CLIP YOUR DOTS, 100% uptime is not impressive if your clipping dots.
It depends on the fight. Some you'll never get 100% due to phase transitions. You should be able to come close on most fights though. This is one place where practice on dummies can help a lot. Don't worry about the DPS figures, just make sure your rotation is solid. Anything from 90% and up is acceptable for a tank and spank. 90% is what occurs if you're letting Immolate drop before recasting every time with 0 haste. If you can get above this then you're doing well. Anything above 95-96% is going to depend on how much haste you have though due to cooldown clashes. Many times ensuring near 100% Immolate uptime is a DPS loss because it requires you to stop casting, which is invariably a larger loss than an extra few ticks of Immolate over the course of a fight. Yes, even if Incinerate lands without Immolate on a target.