The Soul Fragments of the Sorcerers, they will undergo important design changes as we saw in BlizzCon 2009. They will somewhat resemble the runes of the Death Knights.
Ghost crawler You have talked about how you hope the use of these snippets will be. The intention is, that they serve for a crucial moment of a fight just like Heroism / Bloodlust.
If we briefly recall what was said at BlizzCon about them, will quickly regenerate out of combat and there will be a Drain Soul spell to do it in combat. We do not know for sure what all the usefulness of these fragments is, although we do know that there will be a new spell called Burn soul, it will cost 1 Fragment and will have a cooldown of 30 seconds. What it will do is improve the next spell and some will even change their behavior.
Examples:
- Burning pain Improved - The next 3 casts of this skill will be critical.
- Summon Demon Improved - Instant Cast
- Soul fire Improved - Instant Launch
- Fear Improved - Instant Launch
- Spiral of death Improved - Greater Horror, greater healing received
Ideally, we design them so that you don't need to have more in combat. We think this makes Shards more like a cooldown than something you do whenever you have it available. (For example: You generally save Heroism / Bloodlust for the best time, not the first time you can use it.) It is possible that a Warlock could feel annoyed using his last shard just as a group of monsters joined the fight. In that case we will have to add an Evocation type ability so that you can obtain fragments in emergencies.
In a very pure and possibly unreal sense, we would like 3 shards to be spent per combat with some kind of cooldown between each use. I mean non-trivial matches. Maybe you will use a shard on a group of filler monsters and no shards when killing a monster for a quest while leveling up.
What do you think of this to witches? I remind you that you can read more about Cataclysm in the Great Guide to the WoW Expansion.