While I hate to sound like one of the paranoid mages of pre-1.11, who did little but complain about the uselessness of mages during raid encounters that don't involve AoE, that's not something that one mage alone can't do (he could specc full arcane for the slow debuff, and then put the rest in fire for imba imp. scorch for the warlocks! - sorry, just had to). While it certainly is too early to start doomsaying before even seeing TBC raid encounters, I'm starting to get a little worried that we'll once again fall back to being viable raidspots only because we're needed for AoE, and then having it all validated by mana efficency (how this is relevant when compared to a class with unlimited mana hasn't dawned on me yet), the ability to decurse, out-of-combat consumeables and portals.
"Any sufficiently advanced stupidity is indistinguishable from malice."
- Clark's Law
It probably will depend on your warlocks and magi as well, and upon a couple of other factors as well... As far as I can see, seed of corruption is a high mana spell and with Warlocks having such a devastating amount of mana, they'll need to devote cooldowns to Lifetap again and spend a lot of the non Lifetapping time refreshing the DoT's. (Seed of Corruption - 2 sec, Immolate another 2, Siphon Life for another 1.5, if allowed a dmg-ing curse another 1.5 sec. Conflagrate if possible.) I can see this becoming very annoying for magi if the warlocks do it correctly. Then again, their aggro reduce stays abysmal as compared to ours. (Full clear for 1.5 sec cast, 5 min cd against 50 % clear, a Shard and the same cooldown.) I just hope that Invis will actually be a buff, not a debuff, so we can click it off. :P
Why would you use Seed of Corruption over normal Corruption? Corruption can be instant cast and can get 36% of +damage gear additionally added to it.
Warlocks will have the simliar -aggro talents as Mages, there is a 10% less on affliction and a 10% less on desto spells.
Mages have the 8 second wait time aggro clear (Invisibility), Locks have the instant 50% aggro clear every 5 min. Both methods have advantages over the other.
Meh, I overlooked Emp Corruption, still has a 1.5 sec casting time for all it matters. And Invis was changed last beta push according to rumor into a 1.5 sec cast in stead of a 8 sec fade, making it a far more useful spell IMO. (As 8 sec of doing nothing and getting no dmg is a lot, whereas 1.5 is to be overseen and can be handy, even at places where there's a lot of AoE going on.) I'm not overly positive, but I have faith. (And if not, it's still beta, and all things are subject to change. At the least they changed Water Elemental. :P)