DRK Suggestion : Souleater II
Ok as far as i'm concerned Souleater near useless (if not completely)
Either way DRK isn't DRK without this ability so my suggestion is this.
New Job ability : Souleater II (Dark blade)
On use it consumes 40% of your Hp for a 1 min buff which lasts 1 WS
When you WS it'll double your WS damage. could vary with hp.
Recast : Shared with souleater (muted soul could also work on it)
I think this would work well while it wouldn't make drk the no.1 DD it would definitely give it the potential to have the highest spike dmg again.
And yea i know WHMs will cry but they can get 15-25 mp a tick these days so it's not so bad