You left health empty 
Night Fall could use Rech and End.
Slot TT for daamge instead, you don't have too much of that.
Torrent? What For?
If you take PG, give it at least 5 slots, otherwise don't bother.
"Should i have blackhole in there in place of life drain? (as a pve power, i mean?)"
Yes, Life Drain is [censored], black hole is slightly less [censored].
I found Twilight Grasp pretty unimpressive until I got SOs, I would delay it's slotting, but have it 6 slotted by the late 30s.
Tar Patch needs 3 recharge as soon as possible. The slow is unnecessary, you have TT for pinning enemies in place. The reason you want this is for the -res, to make the enemies more vulnerable.
Slot both TT and Night Fall with 6 slots, these are your most effective attacks as they are Cones, they also reduce the enemies to hit significantly. Slot for ACC and damage initially and then add recharges when you get SOs. Using them effectly does require enemies to be closely packed but that is easy using Darkest Night and Tar Patch.
I would put a few less slots in Dark Blast and Gloom.
I would delay Shadow Fall until after stamina, in order to get stamina earlier, you have 2 AoEs as main attacks.
@Unthing ... Mostly on Union.
You should get moonbeam earlier its a really good snipe and slot it with SOs is really strong
Now, first i must mention that i have myself a 3D in hero form. So i have a good background on knowlage of the powers.
(should i have that sooner...much sooner?)
But knowing me its going to be drastically different from the defender sets. So i would like opinions on my intended build. When it comes to slots, that will probably change knowing me.
Archetype: Corruptor
Primary Powers - Ranged : Dark Blast
Secondary Powers - Support : Dark Miasma
01 : Twilight Grasp acc(01) hel(7) hel(9) hel(11) recred(37)
01 : Dark Blast acc(01) dam(3) dam(7) dam(11) endred(21)
02 : Gloom acc(02) dam(3) dam(5) dam(19) endred(36)
04 : Darkest Night thtdbf(04) thtdbf(5) thtdbf(15)
06 : Tar Patch recred(06) slw(19)
08 : Tenebrous Tentacles acc(08) acc(9) immdur(13) immdur(15) thtdbf(37)
10 : Hover defbuf(10)
12 : Night Fall acc(12) dam(13) dam(27) dam(29)
14 : Fly fltspd(14)
16 : Shadow Fall endred(16) endred(17) damres(17) damres(31) damres(33)
18 : Swift runspd(18)
20 : Fearsome Stare acc(20) acc(21) thtdbf(23) thtdbf(23) ferdur(34) endred(37)
22 : Health Empty(22)
24 : Stamina endrec(24) endrec(25) endrec(25)
26 : Torrent acc(26) acc(27) recred(31) kbkdis(36)
28 : Petrifying Gaze acc(28) hlddur(29) hlddur(31)
30 : Howling Twilight recred(30)
32 : Blackstar acc(32) dam(33) dam(33) dam(34) thtdbf(34)
35 : Life Drain acc(35) hel(36)
38 : Dark Servant acc(38) acc(39) hel(39) hel(39) thtdbf(40) immdur(40)
And of course,
41 - Dark Embrace.
44 - Soul Storm
47 - Summon Mistress
49 - Moonbeam ...just for the fun of it
Should i have blackhole in there in place of life drain? (as a pve power, i mean?)
So, who wants to tear it apart?
@Inkwave ..(darn merge)