So, I did some more work, and now it creates pretty graphs.
Simply put, if you enable logging in your combat log, do some fighting, then submit the combat log to the link below, it'll show who did damage to you, with what skills, and what types of damage. This can help you determine what mitigations/corruptions may be useful. It can also take into effect your current mitigations, if you want to see what the theoretical numbers were, and you can play with various mitigations.
It also shows your damage/skill usage, and damage per type and whatnot.

It's not fancy right now, I'd like to make it more interactive so you have sliders or stuff, but comments are appreciated.

http://www.strudel-hound.com/lotrolog/log-analyser.html

Also, please don't break my server :)