I usually take 2 hits to die in heroics. 3 if I am lucky, 1 if I am not. If 2 doesn't kill me I am usually at about <500 hp.
Fade is always helpful regardless of level. It's an "Oh ****" Button and just like all emergency buttons it's a godsend when it's available, it's a death when it's not available.
I was healing H:UP last night with an undergeared tank and fade got quite a bit of use. We knew going in that the tank was undergeared, so we didn't have much expectations. But I was going full on healing (think when a boss enrages, only healing like that on every pull with 3 mobs). Because I was healing so much so often, my aggro skyrocketed and the non-focus mobs would come running right at me, yeah fade was my best friend then. We only downed 1 boss, the Statue boss event killed us, just too much healing needed in that run.
But it was good practice for me, so I didn't mind the deaths, and they were all friends in the run anyway.