If Blade Ward didn't have such an abysmal proc rate then I'd rather view it as a threat/dps enchant than survivability. It simply doesn't proc enough.
I have been debating my weapon enchant choices lately. When Blood Draining procs at the right time, it can be a raid saver. This has happened to me once in 6 months. Which totally is not worth it IMHO. Most of the time it is irrelevant. I THINK it is time to consider threat/dps enchants. ATM I don't quite dare to use Berserking, but a straight Agi/AP/Precision/whatever enchant that is always with you can be quite useful.
But TBH, weapon enchants aren't as important to tanks as they used to be. Choose whatever tickles you fancy. But make sure it doesn't kill you.