OK.. I know you don't want to respec but with inherent Fitness and 2 freebies coming you might as well take advantage of it- I used that and did some tweeking without redoing your build.
Gave you 22.5% extra recharge and a bit more damage bonus. The sets I used are pretty cheap, the most expensive IOs I used were the Stupify Acc/Ends And the 1 LoTG 7.5% (Use Hero/Villain Merits to grab them if need be, that's what I do, you can get the LoTG in a few days and the rest just as fast.)
Your End consumption is a bit higher but not horribly so, especially if you're aiming for the Cardiac Alpha.
(Death Shroud will boost your damage a LOT, trust me, and I run my Dark/Dark with that and Cloak of Darkness no problem either)
Villain Plan by Mids' Villain Designer 1.81
http://www.cohplanner.com/
Click this DataLink to open the build!
Tyrant Nadir: Level 50 Natural Brute
Primary Power Set: Energy Melee
Secondary Power Set: Dark Armor
Power Pool: Flight
Power Pool: Teleportation
Power Pool: Speed
Ancillary Pool: Soul Mastery
Villain Profile:
Level 1: Barrage
- (A) Stupefy - Accuracy/Endurance
- (3) Damage Increase IO
- (3) Rope A Dope - Accuracy/Recharge
- (5) Rope A Dope - Accuracy/Endurance
- (5) Crushing Impact - Damage/Endurance
- (7) Recharge Reduction IO
- (A) Impervious Skin - Resistance/Endurance
- (7) Impervious Skin - Resistance/Recharge
- (9) Impervious Skin - Endurance/Recharge
- (9) Impervious Skin - Resistance/Endurance/Recharge
- (11) Impervious Skin - Status Resistance
- (A) Stupefy - Accuracy/Endurance
- (11) Damage Increase IO
- (13) Rope A Dope - Accuracy/Recharge
- (13) Rope A Dope - Accuracy/Endurance
- (15) Crushing Impact - Damage/Endurance
- (15) Recharge Reduction IO
- (A) Stupefy - Accuracy/Endurance
- (17) Crushing Impact - Damage/Endurance
- (17) Rope A Dope - Accuracy/Endurance
- (19) Rope A Dope - Accuracy/Recharge
- (19) Recharge Reduction IO
- (21) Recharge Reduction IO
- (A) Pounding Slugfest - Accuracy/Damage
- (21) Pounding Slugfest - Damage/Endurance
- (23) Pounding Slugfest - Damage/Recharge
- (23) Pounding Slugfest - Disorient Bonus
- (A) Rectified Reticle - Increased Perception
- (25) To Hit Buff IO
- (25) Adjusted Targeting - To Hit Buff/Endurance
- (27) Adjusted Targeting - Endurance/Recharge
- (A) Impervious Skin - Resistance/Endurance
- (27) Impervious Skin - Resistance/Recharge
- (29) Steadfast Protection - Knockback Protection
- (29) Impervious Skin - Endurance/Recharge
- (31) Impervious Skin - Resistance/Endurance/Recharge
- (36) Impervious Skin - Status Resistance
- (A) Empty
- (A) Flight Speed IO
- (A) Touch of the Nictus - Accuracy/Healing
- (31) Touch of the Nictus - Accuracy/Endurance/Heal/HitPoints/Regeneration
- (33) Theft of Essence - Accuracy/Healing
- (33) Touch of the Nictus - Accuracy/Endurance/Recharge
- (33) Theft of Essence - Healing/Recharge
- (A) Cleaving Blow - Accuracy/Damage
- (34) Cleaving Blow - Damage/Endurance
- (34) Cleaving Blow - Damage/Recharge
- (34) Cleaving Blow - Accuracy/Recharge
- (43) Endurance Reduction IO
- (A) Luck of the Gambler - Recharge Speed
- (43) Endurance Reduction IO
- (A) Accuracy IO
- (36) Hecatomb - Accuracy/Damage/Recharge
- (37) Rope A Dope - Accuracy/Stun/Recharge
- (37) Rope A Dope - Accuracy/Recharge
- (37) Damage Increase IO
- (39) Endurance Reduction IO
- (A) Accuracy IO
- (A) Time & Space Manipulation - +Stealth
- (A) Impervious Skin - Resistance/Endurance
- (36) Impervious Skin - Endurance/Recharge
- (39) Impervious Skin - Resistance/Recharge
- (39) Impervious Skin - Resistance/Endurance/Recharge
- (40) Impervious Skin - Status Resistance
- (A) Rope A Dope - Accuracy/Endurance
- (40) Rope A Dope - Accuracy/Stun/Recharge
- (A) Accuracy IO
- (40) Accuracy IO
- (42) Damage Increase IO
- (42) Damage Increase IO
- (42) Recharge Reduction IO
- (43) Recharge Reduction IO
- (A) Trimuphant Insult - Chance to Disorient
- (A) Endurance Modification IO
- (A) Rooting Grasp - Accuracy/Immobilize/Recharge
- (45) Trap of the Hunter - Accuracy/Immobilize/Recharge
- (45) Gravitational Anchor - Chance for Hold
- (A) Thunderstrike - Accuracy/Damage
- (46) Thunderstrike - Damage/Endurance
- (46) Thunderstrike - Accuracy/Damage/Endurance
- (46) Thunderstrike - Accuracy/Damage/Recharge
- (A) Dampened Spirits - Recharge/Endurance
- (48) Dark Watcher's Despair - Chance for Recharge Slow
- (48) Dark Watcher's Despair - To Hit Debuff/Endurance
- (48) Dark Watcher's Despair - To Hit Debuff
- (50) Dark Watcher's Despair - To Hit Debuff/Recharge
- (50) Dampened Spirits - To Hit Debuff/Endurance
- (A) Recharge Reduction IO
- (50) Recharge Reduction IO
Level 1: Brawl
- (A) Accuracy IO
- (A) Endurance Reduction IO
- (A) Recharge Reduction IO
Level 4: Ninja Run
Level 1: Swift
- (A) Empty
- (A) Empty
- (A) Empty
- (A) Performance Shifter - Chance for +End
- (31) Endurance Modification IO
- (45) Endurance Modification IO
Set Bonus Totals:
- 7% DamageBuff(Smashing)
- 7% DamageBuff(Lethal)
- 7% DamageBuff(Fire)
- 7% DamageBuff(Cold)
- 7% DamageBuff(Energy)
- 7% DamageBuff(Negative)
- 7% DamageBuff(Toxic)
- 7% DamageBuff(Psionic)
- 5% Defense(Energy)
- 5% Defense(Negative)
- 2.5% Defense(Ranged)
- 16% Enhancement(Accuracy)
- 27.5% Enhancement(RechargeTime)
- 118.07 HP (7.876%) HitPoints
- Knockback (Mag -4)
- Knockup (Mag -4)
- MezResist(Confused) 22.5%
- MezResist(Held) 22.5%
- MezResist(Immobilize) 22.5%
- MezResist(Sleep) 29.1%
- MezResist(Stun) 22.5%
- MezResist(Terrorized) 22.5%
- 20% Perception
- 5.5% (0.092 End/sec) Recovery
- 48% (3.004 HP/sec) Regeneration
- 6% XPDebtProtection
"Well, there's going to be some light music and a short note of apology saying, 'The universe ended last week, we're really sorry, we don't know what you're doing here, didn't you get the message?'"- Steve Moffat
Thank you! 
Yeah - end is not fun. Right now I typically keep Dark Embrace, Murky Cloud and Obsidian shield running in a fight, with Dark Regeneration and Darkest Night being the two things that make my endurance drain super fast. Thank goodness for Cardiac @_@
Here's my cute and cuddly level 50 Energy Melee/Dark Brute. Specs from Titan Sentinal, usable in Mids.
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1. Path of least resistance - spruce up the slotting without a respec.
2. Path of "arg" - redo his entire build.
I overall like the way he plays, favoring rate of attack over pure damage, letting Fury make up the difference. Generally speaking +0/x1 he's fine, and I can generally play +0/x2 fine although it is more challenging! His attack chain feels pretty solid to me overall, and I like the way he "feels."
Tentatively speaking I plan to get the Endurance Alpha Boost when i19 hits.
What are some possible optimizations I can go for to improve his performance while not making any massive changes? Right now most of his slotting is centered around being Exemplar friendly and honestly that's something I really want to keep. I'm not overly interested in chasing after expensive sets and Purples, nor being utterly min/maxed. Just want a little more oomph, you know? If he could handle +1/x2 or +0/x3 that'd be nothing short of awesome, but really all I want is to be able to better handle +0/x2 better.
If I can avoid a respec, that'd be nothing short of GLEEE.