Dark Pit needs alot of slots to make it useful. Its accuracy is rubbish and has a long recharge. It will only affect minions aswell.
Shadowfall's best feature is that it gives resistance to psi damage which is very rare. If you are using superspeed on top of shaowfall you will be "invisible" in PvE. Without SS it offers a bit of stealth.
Howling Twilight. Have you considered using this as more than jsut a rez? Its an autohit power that will disorientate minions, plus damage, debuff accuracy and debuff recharge. It is more than just a rez power and can be used as an effective debuff.
Both shadowfall and howling twilight are worth taking at some point so either one of those 
basically what tufty said. Dark blast in my opinion is nothing special, and I heard that dark blasts will have thier acc debuffs taken away.
Dark miasma on the other hand is one of the best powersets in the game for buffs/debuffs.
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basically what tufty said. Dark blast in my opinion is nothing special, and I heard that dark blasts will have thier acc debuffs taken away.
Dark miasma on the other hand is one of the best powersets in the game for buffs/debuffs.
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Where on earth did you hear that? Its the first I've heard of it!
Anyway....
Dark blast - the essential picks (at least in my opinion) are dark blast, gloom, tenebrous tentacles, nightfall and blackstar - any others are either superfluous (depending on your secondary, of course) or just not needed.
Dark miasma, on the other hand, only has two powers that can even be considered below average - black hole, and petrifying gaze, neither of which are in your current level range anyway 
Shadowfall ideally needs 5 slots (2 end redux, 3 damage resistance), but you can add them in later on, as the extra damage resistance isnt hugely needed till the late 20s.
Anyway, of the three, I'd say shadowfall, then howling twilight - but thats just me 
I'd vote for Shadow Fall as well. It's fantastic to have the energy, negative energy, and psionic res from it. Also, the stealth will stack with Super Speed (if you have it, or respec into it sometime) to provide invis against most NPC enemies.
I would disagree with the previous poster about Petrifying Gaze, just for the record. If you pick up a hold from your Patron Power Pool later on, you can stack the two, and hold bosses. Or you can help your team's more dedicated holders lock down difficult opponents, whether than means an arch villain/hero or someone in PvP.
Heh, feel free to disagree with me - I'm by no means a fount of always correct information
Let me clarify then; ON ITS OWN Petrifying gaze just doesn't cut the mustard - but if you have a nother hold to stack with it, it can be useful - I'd generally advise not picking it up till you get to patron level, then respeccing it in in that case, but thats just me - my dark/elec was spoiled by having a second hold in his secondary
By the way Cel, you and Syn 50 yet?
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Heh, feel free to disagree with me - I'm by no means a fount of always correct information
Let me clarify then; ON ITS OWN Petrifying gaze just doesn't cut the mustard - but if you have a nother hold to stack with it, it can be useful - I'd generally advise not picking it up till you get to patron level, then respeccing it in in that case, but thats just me - my dark/elec was spoiled by having a second hold in his secondary
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Mm, it does work better with a second hold, certainly - I'm one of those lucky Ice/Darks who didn't need to wait for Patron Powers. 
I found even when I only had one hold, though, that I quite liked being able to lock down Lts., especially when I was solo. Also handy if you tend to coordinate quite a bit with your teammates - Syn plays as Robots/Dark, and we've always worked together to hold troublesome bosses, EBs, AVS when they can be held...
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By the way Cel, you and Syn 50 yet?
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Yep! I'm feeling a bit lost now, but no doubt the fog will clear in a bit and I'll get back to playing with alts, or maybe start on the Ice/Dark guide I've been thinking about...
With the i7 respect I'm finnaly getting rid of moonbeam from my dark/dark corr. The trouble is what to replace it with. I can't choose between 3 powers, Dark Pit, Howling twilight and shadowfall. Though howling twilight is rather far down on that short lists since you need to use it in combat. And when ppl start droping in combat I'm either already dead or out of there. (I play a villain, we're not supposed to be brave.
)
I play the char mainly as a debuffer and is currently at lvl 18