What's the goal? I suggest one to 2 focus areas.
Such as:
+HP and +Recharge
or
Ranged Defense for the MM
So on and so forth.
I don't see any particular focus with this build.
The one thing that REALLY stands out is that you didn't yake Howling Twighlight. You NEED this power. It is one of the best debuffs and an autohit stun and has a nice little side effect of rezzing multiple teammates if needed.
I use this extremely offensively solo and on teams (hint: you don't need teammates down in order to use it). I don't think I can express here how GOOD Howling Twighlight is. I'd sell my mother for it. Heck, I'd sell your mother for it.
Good luck.
Regards,
Fitz
I agree with FitzSimmons. Slot up IO bonuses for recharge; most of the dark debuff need it. Howling Twilight is as good as advertised by our dance instructor/diet consultant. It totally eats the alpha strike from spawns. It shines on Malta and Sky Raiders.
I think you slotted crack the whip a little heavy. You might want more endurance reduction in your leadership toggles. I am looking at your power selection order. It would be more appealing if you could take Hell on Earth closer to Summon Demon Prince; they are a matched pair 
. Level 28 Hell on Earth, level 30 Pet Gaze, level 35 Assault.
I also on my Demon Prince Frankenslotted him to get some slow enhancements on his delicious frosty aura and ice cone attacks. It isn't soulbound allegiance set bonus, but I used Pacing of the Turtle and didn't give up much Accuracy and Damage.
Triumphant Defenders Forever
Psylenz FF/Psi, ArticQuark Storm/Rad, Symon BarSisyphus Bots/psn, Max VanSydow Thugs/Dk, Cyclone Symon Bots/stm, Blue Loki Ice/Cd, Widow 46526
HelinCarnate:OMG it is so terrible. I have the option to take 3 more powers but no additional slots. Boo F'ing hoo.
Very expensive build but would like to ultimately apply it on my char.
Comments welcome.
Villain Plan by Mids' Villain Designer 1,704
http://www.cohplanner.com/
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Level 50 Magic Mastermind
Primary Power Set: Demon Summoning
Secondary Power Set: Dark Miasma
Power Pool: Flight
Power Pool: Fitness
Power Pool: Leadership
Ancillary Pool: Mace Mastery
Villain Profile:
Level 1: Summon Demonlings -- BldM'dt-Acc/Dmg(A), BldM'dt-Dmg/EndRdx(3), BldM'dt-Acc/EndRdx(3), BldM'dt-Acc/Dmg/EndRdx(5), BldM'dt-Acc(19), BldM'dt-Dmg(34)
Level 1: Twilight Grasp -- Nictus-Heal(A), Nictus-Heal/HP/Regen/Rchg(5), Nictus-Acc/Heal(7), Nictus-Acc/EndRdx/Heal/HP/Regen(7), Nictus-Acc/EndRdx/Rchg(13), Nictus-%Dam(19)
Level 2: Tar Patch -- RechRdx-I(A), RechRdx-I(9), RechRdx-I(9)
Level 4: Darkest Night -- DarkWD-ToHitDeb(A), DarkWD-ToHitDeb/EndRdx(11), DarkWD-ToHitdeb/Rchg/EndRdx(11), DarkWD-ToHitDeb/Rchg(13)
Level 6: Enchant Demon -- EndRdx-I(A)
Level 8: Crack Whip -- Posi-Acc/Dmg(A), Posi-Dmg/EndRdx(15), Posi-Dmg/Rchg(15), Posi-Dmg/Rng(17), Posi-Acc/Dmg/EndRdx(17)
Level 10: Hover -- Flight-I(A)
Level 12: Summon Demons -- BldM'dt-Acc/Dmg(A), BldM'dt-Dmg/EndRdx(23), BldM'dt-Acc/EndRdx(23), BldM'dt-Acc/Dmg/EndRdx(25), BldM'dt-Acc(36), BldM'dt-Dmg(37)
Level 14: Fly -- Flight-I(A)
Level 16: Swift -- Flight-I(A)
Level 18: Health -- Heal-I(A)
Level 20: Stamina -- P'Shift-EndMod(A), Efficacy-EndMod(21), EndMod-I(21)
Level 22: Shadow Fall -- LkGmblr-Def/EndRdx(A), LkGmblr-Def/Rchg(40), LkGmblr-EndRdx/Rchg(43), LkGmblr-Def/EndRdx/Rchg(43), LkGmblr-Def(43), LkGmblr-Rchg+(46)
Level 24: Fearsome Stare -- Abys-Acc/Rchg(A), Abys-EndRdx/Fear(25), Abys-Acc/EndRdx(29), Abys-Fear/Rng(31), Abys-Acc/Fear/Rchg(31), Abys-Dam%(31)
Level 26: Summon Demon Prince -- S'bndAl-Dmg(A), S'bndAl-Dmg/Rchg(27), S'bndAl-Acc/Dmg/Rchg(27), S'bndAl-Acc/Rchg(29), S'bndAl-Dmg/EndRdx(36), S'bndAl-Build%(36)
Level 28: Petrifying Gaze -- BasGaze-Acc/Hold(A), BasGaze-Acc/Rchg(33), BasGaze-Rchg/Hold(33), BasGaze-EndRdx/Rchg/Hold(33), BasGaze-Acc/EndRdx/Rchg/Hold(34), BasGaze-Slow%(34)
Level 30: Assault -- EndRdx-I(A)
Level 32: Abyssal Empowerment -- EndRdx-I(A)
Level 35: Hell on Earth -- SvgnRt-PetResDam(A), EdctM'r-PetDef(37), C'Arms-+Def(Pets)(37), ExRmnt-+Res(Pets)(50)
Level 38: Dark Servant -- DarkWD-ToHitDeb/Rchg(A), DampS-ToHitDeb/Rchg(39), DarkWD-ToHitdeb/Rchg/EndRdx(39), SipInsght-ToHitDeb/EndRdx/Rchg(39), Cloud-ToHitDeb/EndRdx/Rchg(40), SipInsght-Acc/ToHitDeb(40)
Level 41: Web Envelope -- TotHntr-Acc/Rchg(A), TotHntr-Acc/EndRdx(42), TotHntr-Immob/Acc(42), TotHntr-EndRdx/Immob(42)
Level 44: Scorpion Shield -- LkGmblr-Def/EndRdx(A), LkGmblr-Def/Rchg(45), LkGmblr-EndRdx/Rchg(45), LkGmblr-Def/EndRdx/Rchg(45), LkGmblr-Def(46), LkGmblr-Rchg+(46)
Level 47: Tactics -- AdjTgt-ToHit/EndRdx(A), AdjTgt-ToHit(48), GSFC-ToHit(48), GSFC-ToHit/EndRdx(48)
Level 49: Power Boost -- RechRdx-I(A), RechRdx-I(50), RechRdx-I(50)
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Level 1: Brawl -- Empty(A)
Level 1: Sprint -- Empty(A)
Level 2: Rest -- Empty(A)
Level 1: Supremacy
Level 6: Ninja Run
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Set Bonus Totals: