I just wanted to quickly share some observations I have about the IM curse, and some tools I have used to (mostly) stay alive when fighting OK's while playing a Zealot.
OKs tend to act like ranged characters. They will stand still and curse/shoot like an archer. Advancing on them will force them to retreat, and when I retreat they do not follow.
I have found that when soloing areas that have OK's I can run up to them, then turn on vigor and retreat. This will wake up everthing arround the OK, and everything but the OK will follow me. When I geat about 1-2 screens away from the OK (the safe zone) I turn arround and start zealing. If I get hit with IM while I am waking up monsters I just run further, and then switch to cleansing while I wait for the mob to find me.
This method works great against a single OK. When the sorrounding monsters are dead I can engage the OK. Every third "action" by an OK will be a curse. So I wait until I get cursed, if it is not IM I will charge the OK. While charged-locked they tend not to attack.
Problems arise when multiple OKs are present. Charge is again the (risky) solution. I pick an OK, run "behind" it, wait for a non-IM curse to be cast then charge it. This will push the target OK away from the others toward my safe zone. Never push an OK away from the safe zone. If you can't push it into the safe zone push it into a wall or another monster. Pushing away from the safe zone will wake up another OK, you don't want that.
This method is very risky, don't try it in HC. It does not work all the time, but It is a lot more effective than anything else I have tried. The key part of this tactic is the wake-retreat step. It will be a lot easier to take care of the OKs themselves if you first draw out any other threats, eliminating them in the safe zone. The wake-retreat step should be safe for HC, just establish a bigger safe zone before you attempt it. Then you could use throwing weapons to take care of the OKs themselves.
This does not work well in a party. Party members expect the Zealot to tank. Of course, tanking in the presence of OKs is also knows as suicide. In this situation I will charge a single OK, pushing it into the safe zone or a wall. I have yet to find a good party-friendly solution for multiple OKs. I usualy pick them off one-at a time with charge and hope that my luck holds out. I would rather be lucky than good.