I really can't understand how some people have finished the game in several difficulty modes already. I've started playing a few days late but i'm still in Act 1. We must be playing very differently.
Also, I changed my wizard skills a lot over time, and realized that while some of my previous skills seemed mandatory, they could actually be replaced by some other spells very effectively. And whoever thinks that runes make no difference is very wrong. Sure, some of them are not game-changers, though useful, but some others change completely how you use the skill and turn a mediocre skill into a mass murder tool.
Right now (i'm still low level), i'm using frost ray with extra slow for single targets (pretty high damage, and very easy to kite with the slow), Arcane torrent for tough monsters (high dps, long range with some aoe), Frost Nova with shatter (Freeze everything in an aoe, and then creates a new Freeze aoe when one of the frozen mobs is killed), and probably my best skill is the one that sends three bolts of electricity in front of you, with the first rune (killed mobs explode). While i hated this skill at first, it's incredibly good against packs of mobs, especially if some of them have low hp. I was in spider-infested caves earlier, and all of the small spider pack that went after me died with just one use of this skill.
Not only is it free (no arcane cost), it also comboes with Frost nova if you're facing tougher monsters. Initiate with the nova, then spam the electricity and it creates a chain reaction. And it's also super good against small highly mobile monsters (like those sorta annoying green frogs jumping all around in act1).