If you don't have time to spend on crafting or you don't like to wait long for someone to repair your stuff, here is some advice that works for me 100% of the time:
1. Go to the Repair NPC in Ul'dah, near the Aetheryte, or anywhere you see a lot of people gathering.
2. Offer 4000x the grade of Dark Matter -- i.e. Grade 1, offer 4000 gil. Grade 5, offer 20,000 gil.
3. Say this (substitute your actual item rank and reward):
"Could someone please help me with repairs?"
"Armorer. Rank 36 item. Grade 4 Dark Matter. 16000 gil reward."
See how quickly your gear gets fixed.
Simple!
