So there has been a decent amount of discussion lately on the forums on the uniqueness/usefulness of the Warlock curse system as a whole. The whole system could definitely be made more interesting. While this idea is definitely "out there" it would be quite interesting to see the curse system totally revamped next expansion and made similar to Vanguard's bard song system.
What it essentially consists of is a small little interface that allowed you to combine various aspects of a song (melody, chorus, verse, bridge, lyric, etc) all with their own effects, to create a very customizable buff. IE you might have a "kiting song" that increases movement speed, reduces the effect of slowing debuffs on you, and increases your damage. You could have any number of bardsongs all with specific uses. For example: http://www.vgbards.c
While that system was a little more in-depth than WoW might require, it's a really good idea.
-Afflicting components (debuffing effects): Elements, Exhaustion, Tongues, Weakness.
-Demonic components (affects the characteristics of the curse itself): Quickening*, Spreading*, Eternal*, Potency*.
-Destructive components (damaging effects): Agony, Doom, Punishing*
*Quickening = 20% shorter duration curse.
*Spreading = (hits all enemy targets within 20 yards of your target but has a shared X minute cooldown amongst all curses with the spreading component)
*Eternal = 20% longer duration curse.
*Potency = 10% stronger effect.
*Punishing = Thorns type effect.
So, say you want a pure damaging curse? Create a "Curse of Quickened Elemental Agony". Or Curse of Potent Elemental Doom.
What if you want an anti-melee curse? Curse of Eternal Punishing Weakness. Or Curse of Potent Exhausting Agony.
Anti-caster? Curse of Potent Agonizing Tongues (kinky!)
How about a "fuck up a large groups of enemies in a BG" curse? Curse of Spreading Exhausting Agony. Etc.
Each Warlock could have, say, 5 curse slots which to customize. To make changes to your curses you might have to visit the Warlock trainer. Amplify Curse could be changed to give +1 curse slot. Other talents could add a new component to a curse, new expansions could add a new component, difficult solo quests could reward a choice of a few components, etc. This whole idea could go a long way towards making curses much more fun, customizable, and potent. Would it be a mess to balance and implement? Probably. But it would create a dynamic in the Warlock class that we currently don't have and I, for one, would love to see something like this implemented.