Just a quick one about the Wizard, I don't use anything that requires me to stand around. Standing around is generally a bad idea in the later difficulties. The mana cost for Arcane Orb can be lowered till it's spammable, so my main skills are Magic Missile (for mana recovery), Arcane Orb (main damage dealer), Venom Hydra (passive damage dealer), Blizzard (for kiting), Diamond Skin and lastly either Frost Nova or Magic Weapon or Teleport depending on the area I'm playing in.