I posted this in reply to the latest news post, but I recon we could get some decent debate about it in it's own topic......
Having played a few other classes one thing I did realise is that Warlocks don't actually have any big Damage Multiplying Cooldowns (eg, Dancing Rune Weapon, Blade Flurry).
An idea would be to be able to "use" a shard for a damage buff for a short period of time with a larger cooldown.
This could be implemented as +damage for us:
"Dark enrage" - Tap into the power of a soul and deal 50% more damage for 10seconds, 5 minute cooldown
Or maybe even summon an extra, aggresive pet (could be of ghost form):
"Raise Soul" - Raise the soul of a recently dispatched enemy, causing him to attack your opponent for 15sec, 5 minute cooldown.
A really cool feature of this could be that the soul comes in a ghost form of the actual enemy that you stole the soul from.
I really like the raise soul idea, but they need to find a way to make it totally different to a DK's ghoul...
Of cause this may cause damage balancing issues and we may need to take a slight nerf in overall damage to make up for it, but that's cool. I'd much rather have a few cooldowns that require a bit of skill to nail.
Stuff to think about anyway