I'm using both. (Yes I carry several weapons with different enchants)
In my avoidance set Blade Ward is brilliant for the "boost" to parry.
Blood Draining however is the enchant I use for heavy hitting bosses or fights where I need to survive with blowing my cooldowns.
The 30% save heal is effective to say the least considering it is guaranteed, whereas the Parry proc is merely avoidance.... avoidance is a % at the end of the day.
In saying that what others have said here in regards to Mongoose, yes it is best overall but some fights require different approaches.