If I'm not mistaken, the knights have a DI self only.
You are mistaken. Necros, paladin, shadowknights and clerics all have self only Invulnerability spells, which are absolutely useless for anything but jumping in the Hole pre-20k hps.
They make you invulnerable, wipe you completely off aggro list and last the whooping 18 seconds or so, during which you cant cast, cant attack and can't even scratch yer arse.
Only Clerics have Divine Intervention, which basically gives you second life upon dying.
Druids should get a massive DS (possibly one that scales with the guardian charm), their HoT epic click needs to be looked at, and frankly should get an insane amount of dots that all do reasonable damage (I remember the fun I had rooting/snaring a mob and just loading dots upon dots on it and seeing it die).
