Tanking enchants, especially on weapons, have always been an odd one.
Blood draining is only of value (like activating ardent defender) if you think you are going to die and can potentially be wasted by hit A that took you to 10% health when hit B is the one that killed you. Yes heals add up, but if it's this close to the wire you are probably on heroic lich king. Newsflash - hes going to kill you anyway.
Regarding blade ward - last time I checked you would be doing very, very, very well to be starting to see significant diminishing returns from parry (which have been reduced to be in line with dodge DR), especially when you just reforged half of it to mastery.
Paladins may favour dodge, as it gives them mana back (as if they need it) but warriors on the other hand should favour parry due to the Holding the Line talent. A blade ward proc to a prot warrior means - 600-800 free damage, a near guaranteed parry in the next 5 seconds, this leads to 10% increased crit and crit block chance, and the parry has a 20% chance to increase your physical damage by 10% for the next 12 seconds from Bastion of Defense. In other words avoidance just got interesting.
For bears it's blood draining all the way. They only really have their health now that the idea of stacking agi for armor is dead.
DKs have their own free enchant.