I hear you. But you can't make a statement that "(it) is generally regarded as a less than optimal trinket because it provides a rarely-occurring proc" then. That's just plain wrong,
the rarely-occurring proc is not the reason that this trinket is considered suboptimal.
But anyway, I did also respond to the actual topic, and I disagree with your judgement of the 35% mechanic.
Now, in the LK fight, Mongoose will definitely mitigate/avoid more damage than Blood Draining. It will
likely mitigate/avoid more damage than BD will heal for. This doesn't tell much about tank death prevention.
Mongoose may or may not prevent one or more tank deaths by avoiding the killing blow. BD is very unlikely to save you from death on its own, but it helps your healers and your own cooldowns to save you. So just like Mongoose, it may or may not save your ass.
I don't believe it's possible to really calculate which enchant is 'better', unless you know every single variable of the fight. And then you wouldn't even need a weapon enchant.
