Is there a macro/addon that lets you know ( IN BIG LETTERS) that Fel Spark has procced? I've noticed i've missed a few by noticing they procced too late :S
No macro, but you should be able to configure Power Auras to do something for you. The wiki is here: http://powerauras.wikispaces.com/. Just get the name of the buff that comes up when Fel Sparks procs, then add a Power Aura to account for it - you could probably do a string of text, not positive, but you could at least have the Fel Sparks icon enlarged somewhere on your screen that would alert you.
New Power Aura
Use Own Texture Checked
Buff
Fel Spark
Enemy Target unchecked
Stacks tab - show stacks checked, relative to aura: Center
Timer tab - show timer checked, relative to aura: Bottom
Close
Go to target dummies
cast Immolate on everything
Wait.
Adjust as you see fit.