Get rid of pettwisting, either by buffing the Felguard or by making DS dependant on spec (with the exception of the VW and Succy) although that would be a messy solution.
A flying demon mount!
If I was greedy a blood boil type spell for aff that nukes all dots for a bit of burst, terminating them and causing all dmg that would of been caused to POP (w/ a cd of course).
A Jinx effect on CoT, having same as CoE would be OP. Maybe double the effect if afflicted w/ UA
A lil more punch to Fel Flame (just a lil)
Increased range on port (FFS its a stationary position which enemies can see), or make it invis to enemies
Demonic Shell. Take reduced dmg but unable to move for 6 seconds (we really need more then a port or iHoT to counter melee, just something)
Giving the felguard a new armor and a new axe would be interesting imagine a felguard in full warrior set charging at you with a shadowmourne ( you got the idea... )
For the succubus a new outfit and a new Lash.
For the Imp a new ring and maybe new color ( why not ?)
For the felhunter maybe new tentacle/antenna skin.
For the void walker maybe some symbols on his armor and a color change !
Thatz my wishes !!!
PS : And a permanent DEMON form for Demon warlock !!!