I have to say I love using Firestorm, the constant knockdowns and damage make it an incredibly fun skill, and the fact all the damage is done over the course of the duration makes it very handy for extended fights, even if not so much for burst.
Then again I have to say, I don't know how well the skill works without flashpoint, the RNG gods graced me with a staff that has 16% crit chance and I recently got a 5% critical chance ring, without that constant proccing of flashpoint I wouldn't be able to spam the skill nearly as much as I do now. On my second leveling run with my Ele and my current skills are
- Immolate
- Wall of Fire
- Firestorm
- Fade Cloak (screw you demon commander)
With this set up I have been able to blaze (get it? It is a fire joke) through threatening, I haven't tried my hand at perilous with the ele yet, but I figure that because he sits in the back row he will be basically the same. So far the only thing I have been considering changing up is switching out Immolate for Stone Fist, but haven't tried it out yet to know how well it actually performs.
Strategy wise I pretty much spam Immolate and Wall of Fire at the start of every group, when I proc Flashpoint (which is all the time thanks to my staff) I will toss a firestorm out before waiting on the proc again. At the final room, you can pretty much stop any enemies from getting through the door to the font room with this set up, and punish all those pesky archers who try to group up by it. You ever seen a group of archers constantly burning from a wall of fire, panicking and desperately trying to escape the meteors raining down on them? I love the smell of roasted Venatori in the morning.