you can keep Steal Essence if you don't learn Cripple Attack(single target attack/debuff)... I did this on My ISS Doomcryer to pull non-social MOBS, instead of running into groups of Aggros. However, after awakening the casting is too slow if you take the Superior Armor Masteries... and Damage is very low so I don't think it could be a primary attack unless you really Max out M.atk and Cast speed.
Don't make a Dominator unless you are already in a good clan. If your going to play an Orc mage then just do a Doomcryer. Your gonna look like a bot at the lowbie lvl's while lvling up though. So either way thank's to Awakening all the ISS are the same and your really only choosing the race you want for it.
Dominators are useless anyways since everyone already has a boxed non Dominator buffer following them around.
I would rather say they are not useless, my main is a domi, current hero. I love the class i have tried others but nothing beats buffing u clan mates during mass times at dragons, sieges, etc. With the right step up on that class he a very hard char to beat, espically for oly. Theres a few out there that have them for buff box, but im seeing more other iss classes, being use as buff box.