LOL I tried to +6 several helmets and one got to +5 and the rest poofed going +4. On the plus side I was able to make a +6 boot for a C grade set AFTER giving up on the helmets.
I'm in that exact same boat. So far of 8 OE attempts I have succeeded 3. Of those 3 successes, those were solely +4's. Each and every one went Kaboom trying for +5.
its not 2/3 on armors even if NCsoft says it it. if you look at (you know what homepage) the statistics say its closer to 50%. so getting a +6 armor piece would be 12,5%. if you ask me, its even harder.