really, i've hand no problem on pure lightning tree. i abandoned hair-lip steve for Andronikis the moment i got him and have been just aoeing everything into dust while leveling. and once you get lightning storm, everythings over because you can proc a free chain lightning(that has a good chance to then proc another chain lightning for free) and between the storm and niki's grenade, mobs of mobs are no real worry. you can have a tad bit of trouble with elites, but, especially against melee opponents, you can develop easy ways to keep them away from you long enough for all the damage they will do to you to be negligible.
and, even though it seems a useless talent to some of the sorcerers i know, backlash can be an *** saver when you have it. also sets up a rather amazing opening for tumult