It is still only given a 12. I dont know when you have plans on making in a 15. Let me tell you WHY it should be 15.
Blade Ward:
Tank at full health. he has 100k threat above everyone els.
The buff proccs, you parry the next 10k hit. You get 13k overhealed. You are still a full health.
It inflicts 700 damage. You gain 1k aggro. That 1k you wont feel in your 100k above
Blade Ward:
Tank at full health. he has 100k threat abover everyone els.
The buff doesn't procc, you dont parry a 10k hit so you are down to 30k health. You get healed for 13k (3k overheal). Your are still at full health.
Blade Ward VS Blood Draining at 40% health:
You look at a boss that hits you for 9k-11k. You have Blade Ward. you are soo hoping for blade ward to drop but you dont decide when i proccs. you get hit for 10k and are down to 7k health. you get hit for 9k and healers didn't get a healer on you. you are dead and annoyed that your enchant didn't procc.
Same envirement as before. You have Blood Draining with 5 Stacks. You get hit by 10k and are down to 7k. you heal for 2k cus of you enchant. you get hit by 9k and have 135 health left. you get healed for 13k of all your healers at the same time. you are at full health and love your enchant.
Thats why you should choose blood draining.