I have now made around 15 sets of armor, and I still haven't gotten the achievement for having 10 in your arsenal. When are these going to be fixed?
EDIT: Apparently all the other achievements are coded differently. The armor one you have to have actually 10 pieces of armor in your inventory at ONE TIME, not just 10 throughout like the other achievements.
You have to get ten new pieces of armor since achievements were implemented and it only applies to armor, not helmets or shields. Ones that you had prior to the achievements rolling out did not count.