Blood Weapon / other DRK suggestions:

[Cabalabob]

personally id like drk to get three things in the future.

1. an on demand self heal
Pld has clemency and wars designed around self heals so that's a given but drk self healing is either something you cant use when you need or is too weak to heal you enough to waste mp for, yes abyssal drain is good but only when you've got multiple adds on you as such id like there to be something i the case you need hp (like living dead for example).
best thing i can think of is either a new skill for it or modify unmend to be DA'able to drain and get back a more significant amount of health.

2. Utility
at the moment drk really lacks anything impactfull to the raid (reprisal being useless unless you take dmg or delirium which is useless if you have a monk)
as for what to do for it, thats tough though ive thought id be pretty fun if drk could boost
dot damage for the raid and from there alter delirium to either stack with dragon kick or even allow drk to keep up dragon kicks full effect once it has been applied by the monk and finally allow reprisal to be dark artsable to activate, possibly at an mp cost unless it procs.

3. another dark arts skill
i think one problem ive had with dark arts is i always feel its more useful to use for offensive purposes (not saying not to use it for defensive skills but its something at times if you wanna keep dps up, might just be the way ive been with the job)
one way i was thinking was to add a second one which can only be used every 20 seconds at half the cost, could even add a future skill that requires two dark arts stacks to activate making the skill.

of course theres alot of ways square could go with it, most of all id just like to see all the tanks be able to ot or mt in the future.

Rather than more utility I'd kind of like DRK to just have the highest OT dps to make up for the fact it has no utility. Maybe increase darkside to 20% damage to match WARs maim and change dark arts effects on some of DRKs cooldowns when not in grit to add more damage potential, e.g. Dark arts dark dance in grit will be the same as it is now, but without grit, instead of increasing evasion, dark arts dark dance will add a 20 potency additional hit to all skills. Dark arts dark mind in grit same as now, dark arts dark mind out of grit adds 10% crit rate. Etc.

As for a self heal, I personally think souleater should drain 25%(50% with trait) of damage dealt as hp even without grit, then with grit it becomes 50%(100% with trait) and the same should apply to abyssal drain.

Because I'm not too bothered about DRK not having a self heal and more bothered about the fact it only has any self healing in tank stance which is something neither WAR or PLD has to deal with. Yes WAR only gets IB and equilibrium heal in defiance but it still has storm's eye, thrill of battle and access to second wind even in deliverance, while PLD always has access to clemency. DRK outside of grit only has abyssal drain and as you say this is only effective if you have a ton of mobs hitting you, at which point you'll probably be in grit anyway.