Imo
at 95

Drain I should give the same effect as Cure III (180-200)
Drain II should give the same effect as Cure IV (250-360)
Drain III Should give the same effect as Cure V (360-600 (heavy based on skill))
All w/ a recast of 60 secs

As for the Hp boost i'd say just remove the effect from Drain II and make it a 3-5 Min Job ability you can stack w/ any drain

Even tho i'm sure SE will think this is overpowered but as most DRK know when ya casting your not DDing anyway and you'll still be subject to resists, silence and interrupts being on the front lines so it's not even that bad.