Good but takes 5 - 6month of farming alot, specially the last 2 ranks where you need to play for a straight 2 month 16-20 hours a day to hit the required standing.
Warrior only one that benefits that much from r13.
Other classes get like 20 stamina for the 2 set of epic gear.
If you are a casters, then going beyond rank 12 is meaningless because once naxx or t2.5 is out, you can get gear that is better than the shoulder head and chest reward.
Depends on your role.
For hybrid DPS the PvP sets are made obsolete by T2.5.
For pure DPS, healers and tanks T2 is already better.
For PvE the sets are budgeted with far too much stamina, and while decent for PvP your extra health still won’t win you many fights against a three minute mage.