I've been working on giving the equipment sections in the Wiki a bit of a functional overhaul, and now armor and helmets have stat tables and individual item pages. I'll do the same for weapons and shields soon. Now we just need people who own armors to add the stats!

My own experience is that all helmets and armor items from the same set have the same stats (with the exception of abilities), so essentially you could take off anything else you have on that would modify your stats, and then divide the numbers in your equipment window by 2. If anyone finds a set with a helmet and armor that have different stats, you can just replace one of them with an item you already know the stats for and subtract them out accordingly.

The standard I've set is for the stats to come from level 10 items. I doubt anyone cares what the stats are for items below that.

FOR ITEMS THAT HAVE ABILITIES THAT MODIFY A STAT:
Make sure you subtract the amount the ability adds! Below are the descriptive words and their equivalent stat increases that I've figured out, if anyone else finds out the others post a reply and I'll update the list.
- Moderate: 10