Diablo III: Reaper of Souls

Diamond gems added a little bit of room on armor and helm slots, getting AR is a good option if you need the toughness and CDR is pretty good depending on your build.

I completely forgot about Diamonds, mostly because I main a Wizard which means AR is completely useless (All my Resists are over 1,000 and I have like 1 piece of AR gear). Which just proves that there's more problems with the system. Why is there a gem for AR, but not for Armor or Dodge? Plenty of other stats that are just missing, like Block Chance/Amount, which would be great for a Crusader and would go really well with their Passive that deals with having filled slots.