Question.

[Donquixoth]

I think you should have a look at this post. It compares the damage reduction to armor.

http://www.spacetimestudios.com/show...ction-Analysis

I think that data already outdated by now, because awakening stuff and newest pets. And also it only based on level 41.

[voidPtr]

Yes, it depends on lvl. The info in link is probably still valid, but only if you are 41. At 61 more armor is needed for the same DR. And at 17-18 - less armor will make same DR.
At lvl 17-18 munch mouth's 228 armor better then 4% no argument.