I'm running a wizard with a CM build in act 2, I've botted overnight a few times without any deaths at all. Gile's combat routine is a must, it works much better than the default routines.
With prismatic armor on, I have roughly 9k armor, 800 AR, 30k health, 30k dps, 45% crit chance, 18apoc, and a shield with 20% block.
I just have the standard CM build which is
diamond skin - crystal shell
frost nova - cold snap
explosive blast - chain reaction
energy armor - prismatic armor
energy twister - storm chaser
spectral blades - deep cuts
I know having both spectral blades and ET is a bit weird, but I saw it recommended in another thread and it works surprisingly well for botting. Occasionally the bot will mess up and run out of mana or something, and the spectral blades are a great saver because they still have decent crit chance, do good damage, and also proc the extra tornado from storm chaser.
A wizard champion farmer could probably be made for pretty cheap, although I haven't really tried setting up a new one with cheap gear. Since the wizard's survivability is based off of skills so much, it could theoretically be pretty cheap to make one. I'd say that if you just get a chantodo's will plus a helm with apoc, grab a decent shield, and then stack crit chance up to 40%+ and get a bit of vitality/AR you should be fine. The interesting thing is that you don't need any LOH, my wizard has absolutely zero loh or lifesteal and it doesn't really affect his deaths at all.