End game, Dark struggles with Energy damage. You have to think of it more like a controller meets melee. Dark/dark is more so. Outside of Dark, Claws would be an easy sub in as it is end friendly and has fast enough recharge to where you don't need to add much. You also get two powers with 100% KD/KB. Outside of Claws, anything which stuns so it can stack with the aura. The heal is essentially best in game, but before IOs the end cost was incredibly unkind. Now, you stick a Chance for +End in it and you are practically good to go.