I think it's more than 1, but I don't bother much about it. Obviously attack speed will help with that, but your AP regen will have to be higher to sustain your AP. Magic Weapon Conduit helps with that for big groups but not much for single target.

I gave Zwizm's build a try and it worked very nice. Quite a change of pace from what I was doing which involves kiting a lot. Not maxing CDR at all, just using Evocation and 90%+ Leoric's Crown with a Diamond for 1 sec Frost Nova round robin. Nova lockdown is not perfect for RGs but good enough for me. I did some small changes to it tho:

http://us.battle.net/d3/en/calculato...YO!iShb!YZccZY
http://us.battle.net/d3/en/calculato...YO!RShb!YZccZY
http://us.battle.net/d3/en/calculato...YO!eShb!ZacbZY
http://us.battle.net/d3/en/calculato...YO!WShb!YZcaZY

My 2 highest dps wizards use Black Hole Spellsteal to boost their dps a lot more. The other 2 use Event Horizon and Supermassive to deal with some annoying ground effects and pull even more mobs. They all have roughly the same CDR and casting Black Hole at the same time, so no point on having more than 1 Event Horizon.

The 2 highest dps wizards use Meteor Comet to proc cold but the 4th uses Blizzard which is instant and Frozen Solid freezes which helps me initiate from long range. 1 Wizard will use Blizzard Lightning storm which adds a 15% lightning debuff. I still need to test if this debuff means from ALL sources but regardless, it's still a nice debuff for a single wizard. That wizard will replace Electrocute with Magic Missile Glacial Spike which also freezes. My last wizard uses Magic Missile Seeker just to proc Arcane since it uses Black Hole Supermassive.

Passives are straight forward, but I went with Audacity for my main for higher dps. Since I'm already fighting at melee range, Audacity is a multiplicative buff which adds more dps than Glass Canon. I'm using Unstable Anomaly since my Esoteric Alteration is at rank 1 and I'm getting raped by ground effects.

With this setup, is easier to get close to a pack to freeze lock them. Blizzard from range to freeze, Black Hole and then move right next to them to finish the combo.