what is your crit hit % and crit hit dmg?
on my wiz i'm able to solo t3 i haven't tried t4 yet because i've been playing on my barb.
http://us.battle.net/d3/en/profile/s.../hero/43297736
those are the spells i use and passives. i'm at almost 50% crit hit and 339% crit damage increase on my wiz - i think i'm at about +10 arcane power for crit hit so when a huge mob appears - black hole and hold right click for my arcane torrent cascade which i can pretty much just hold down without running out of arcane power. i have a lot of room for upgrades on my wiz though.
i think if you were to re-roll some stuff (weapon vitality for socket. I think you have more than enough toughness and life you can sacrifice some of that for damage. get a socket to gem it with an emerald.) try to put more of your spells under one type of damage and then you can re-roll some of your items or gamble for items with "increase x type damage by X%" or re-roll some of your spell damage stuff (eg. increase damage to arcane torrent by X%) easier on rare items and cheaper vs legendaries and sets.
if others can chime in to help you that would be great as well because I don't think I am that knowledgeable in this game.