All the same badstuff from the datamined notes but some differences:

Souleater reads "A portion" of damage dealt is returned. This could mean any %. We'll have to test in game in six hours.

Dark Arts Abyssal Drain now also reads "A portion", which makes me think it is no longer 100%, otherwise it would read something like "Returns all damage dealt as HP" or something like that.

/sigh

http://na.finalfantasyxiv.com/jobguide/darkknight/