Last evening I was talking to a friend who is in a guild that is currently attempting C'Thun. Their Warlocks are currently discovering that wow, they can actually do damage, and that the 16 debuff limit needs to be taken into account during raids.

So, one of them found this thread called "The Warlock's Guide to Raiding" on the WoW forums:

http://forums.worldofwarcraft.com/th...11381260&sid=1

In post #4, the author says the following:

Now, my gut feeling is that the invisible debuff slot remark is not true, but I am not sure. Maniq mentioned something about Rain of Fire being "Persistent Area Aura: Periodic Damage" and that debuffs are "Mod: Apply Aura"; can anyone confirm or, even better, explain that this means it doesn't cost a debuff slot?

I can confirm that the arcane missles thing was true for a while, way back in the day. Not sure if it's still true, but I doubt it is. The same was true for every channeled spell back then, including drain life and such.

There is some concept of invissible debuff slots. If you as character get hit by say rain of fire of a mob you see a CHAT_MSG_SPELL_PERIODIC_SELF_BUFFS fired. Look at SCT, and you see ("Rain of Fire") float above your head.
But that debuff doesnt show up as actual debuff.

Drain life has a visible debuff. I know that was the case for mind flay at least from open beta onwards, so if those ever had invisible debuffs, it was in closed beta.

It's very true. While some channelled spells have a visible debuff -- like the warlock drains and mind flay -- many of them do not. Hellfire, Raid of Fire, Blizzard are some other examples. Try being a shadow priest on corehound packs and you can really see this. SWP should last for 24s, but by the time you get back to the first mob (that's casting SWP on every hound, the poor man's AoE), all the SWPs have either been knocked off by AoE spam or some of them have while others retain it. It's very frustrating ;)

Ugh, weird double post. Yay.

My fault, I phrased my answer wrong... I know drain life has a visible debuff, I was trying to say that all channeled spells occupied a debuff slot, just wasn't sure if they still do because I no longer play a caster. :)

Oh.. i didnt hear about it becoming 40 slots, when/where was that announced? And i definately agree that its still not enough :P Not even 2 slots per person.

Tanks and healers won't be using a lot of slots, and I'm sure Druids can live without moonfiring. 40 slots should be plenty. Anything 'good' will fit.

I still say they should seperate personal debuffs that mainly do damage from group debuffs that act as force multipliers.

Effectively...pretty much every DoT in the game(Deep wounds, SW:P, the warlock lineup, etc...etc...) should really not count towards the debuff limit. Only things that directly affect group/mob functionality. Just have the first debuff slot contain a drop-down list of all DoT's currently affecting the target and after that you have all the good old faerie fire, curse of recklessness, sunder armor, etc...etc...debuffs that either drop mob dps or increase raid dps and whatnot.

Now we will have Mangle in addition to Rip and Rake. And the useful Faerie Fire.

Totally agree. Though, I thought the limit was in place due to hardware limitations?

If they ended up reducing the number of useful debuffs by stacking damaging debuffs ontop of eachother (and you'd actually need a few stacks; one for all the schools and one for physical), they'd end up doing something whacked like with ignite where the first effect applied is simply multiplied for everyone added... if it doesn't work like that, then what's the point? They might as well just remove all the restrictions and be done with it.

I know in Warcraft 3 they coded their AoE spells to just put invisible DoT debuffs on units inside the AoE range, and I'm very sure that's what they've done here too. We also know from the old Twin Emps and Grand Widow that the duration and reappliance of this DoT wasn't always so forgiving.

Though AoE spells and Arcane Missiles are invisible debuffs, they don't appear to take up the regular debuff slots. I know Arcane Missiles used to, but I don't think it does anymore.

I don't know, Blizzard has been extremely liberal with the debuffs and I can really imagine 40 not being enough in a 25 man raid. Affliction Warlocks alone can comfortably use up 5, then there's Shadow Embrace, IBS, Drain Life, etc. I guess we won't find out for sure until this content comes out. I certainly hope Immolate and Corruption are being boosted to "you can't knock this off" status like Curses at the moment, since Destruction and Affliction respectively are going to be relying on these for their damage.

"Good" stuff that could be up, given one person speccing into each tree of each class:

Druid:
Insect Swarm
(Improved) Faerie Fire
Rip
Mangle

Hunter:
(Improved) Hunter's Mark
Expose Weakness
Screech

Mage:
Slow (maybe)
Winter's Chill
Improved Scorch

Paladin:
Judgement of Light
Judgement of Wisdom
Judgement of the Crusader

Priest:
Shadow Word: Pain
Vampiric Touch
Vampiric Embrace
Shadow Weaving
Mind Flay

Rogue:
Hemorrhage
Deadly Poison x3
Rupture x3

Shaman:
Nothing?

Warlock:
Corruption x3
Immolate
Curse of the Elements
Curse of the Shadows
Curse of Recklessness
Siphon Life
Unstable Affliction

Warrior:
Sunder Armor
Deep Wounds x2
Demoralizing Shout
Thunderclap
Mortal Strike

Total: 40

I probably missed a few, and there's a bunch of short-duration things I skipped, but even with 27 people in the raid you could theoretically keep everything that's actually useful up. If people are using things intelligently, there still won't be any space for serpent stings and other random garbage, though.

And let's not forget the things that will be put up that you can't avoid. Like the fireball dot (WTB: talent that rolls the fireball dot into the direct damage), the pyroblast dot, the ignite dot and impact. That is a lot of stuff, and we are talking about only one fire mage.

I can't imagine a boss being stun-able (and if you're worried about 40 debuff slots on a trash mob... you shouldn't be), and I don't see many mages using pyroblast. So you're talking 3 debuffs from a firemage (include scorch vulnerability). And 1 from an arcane mage and 1 from a frost mage (arcane missiles and that +crit debuff).