Well not sure how many times someone has spoken about this topic but going to put in my 2 cents. Just a few changes in the tree I think that would be good and still not OP the class.
I also play demo full time so forgive me if I screw up all your cookie cutter build users.

Demonic Empathy needs to just be overhauled; My idea would be
Increases summoned demons haste/hit rating 33/66/100% of your haste/hit rating.

Reason: A very well geared Demo lock is balancing hit/crit/haste for raid spec. Allowing this feat can actually increase our DPS without making OP for PvP.

Improved Enslaved Demon: Overhauled
1a. Increases duration time of summoned DG/(what ever I fire elemental looking demons is) for 3/5 min and Metamorphosis 45/1min.
1b. Same as above but with the 5 min spec the addition of considered as a summoned demon for the time limit. Which would mean we gain all the buffs we have talented specced as we would same as any other pet.

Reason: What can I say it was worthless talent before; At least now we actually have decision to make while being a demo.

Grim Reach and Destructive Reach
1a. Needs to be changed to 15/30%
1b. Moved to tier 2

Reason: For a ranged DPS our range is lacking. Will increase overall DPS for the class in general by lowering our movement for a casting times. etc. (Moderate help in PvP)

Siphon Life
Move to tier 3

Reason: Like all the other talent tree skills are in Tier 3 Shadowburn and since you moved up Soul Link for whatever reason you want to call it. Share the love. Everyone wants survivalability we want alittle more DPS. Win Win situation IMO.

Metamorphosis
1a. Allowed to be used while stunned and clears all stun and snare effects on initial change. After that same as it normally is.
1b. While in this form gives a Demonic aura to party/raid thats near you. what this does is gives everyone the same effects as us in demonic form.

Improved Fear: Overhaul
1a. Change to while feared snared by 35/75%
1b. Change to while feared they are petrified(AKA rooted) and then when fear wears off snared 15/30% for 10 sec

Reason: Considering everyone has immunities to it and Residule effects on it why not. Also our main problem while even trying to kill someone while there feared they are out of range before I can even get off 1 nuke and thats if we get fear to stick.

Lastly just a wishful idea some kind of melee immunity that lasts 10 secs that we can use with a 2 min CD. We currently have no immuntiy and no resistance. I don't know whos idea this was but its the reason why warlocks are complaining about PvP. Every class has either Very high resistance to shadow or fire or has some type of spell immunity mostly to fear that last 10 sec or more. That can be used even with fear on them.
For a ranged dps class you are allowing all melee to get within our range because of these immunities. Only way to balance this is to give us our own type of immunity and that would be to melee only. It won't stop those 5K holy bursts or those DK auras but it will stop those CoS rogues that stun you for 10 sec then CoS so you can't hit them with anything fast enough to kill them before you. (Balanced my yang).

Feel free to responded or point out what you think would be better. Just looking for some constructive ideas that maybe Bliz might consider to implement rather than all the complaining about whats broken.

Also I left out curses for a reason thats a whole other thread lol

Shamrocks Cairne