The golden levels of each class!

[Synthlol]

Cleric - Level 39

Complete Heal, enough said.

Wizard - Level 29 or Level 51

I'd say this is a toss up. At level 29 you get Bonds of Force, which basically enables quad kiting. You can do it without a snare, but it really, really sucks.

At level 51, you get an upgrade to Bonds of Force, Atol's Spectral Shackles. It's gives you a little stronger snare that lasts a little longer, so that bumps your efficiency up. You also get a new single target nuke (Draught of Fire) and a new quad nuke (Pillar of Frost). Both of these new nukes are just miles ahead of the spells they replace in efficiency, so this is probably the biggest jump in kill power a Wizard will ever see other than getting their hands on an item with a strong clicky nuke.

Necromancer - Level 49 or Level 51

Level 49 is huge for a necromancer. You get a new version of basically every single one of your main spells. New pet, new lich, new lifetap nuke, new lifetap dot, new undead only nuke, new undead charm, new fire dot, new snare dot, and your 3min root.

Level 51 deserves an honorable mention because Splurt is just that OP.

Monk - Level 50

Or whatever level you can equip and click the epic.