As we approach Classic I'm doing research for my guild about what works and what doesn't. I personally have not played Classic nor played on any private server (beyond like level 15 just to see what it was like) so nearly all of my information is coming from other sites and videos.
This came up in officer chat the other day and I realized that I'm not sure of what the raid composition/disposition is for Vanilla WoW. What I mean is, in modern WoW you would need like 2 tanks, 3 healers, 5 DPS (for a 10-man raid) and you can build a team around those numbers. Is there a similar sort of role breakdown for Cassic? Does it vary by a large amount per raid, even per boss? I know, for example, that 4 Horsemen requires 8 Warrior tanks but would that automatically translate to wanting 8 warriors in your raid team at all times? I'm more interested in the sort of role breakdown than necessarily a "perfect" composition (e.g. 4 Shaman, 6 Mages, etc.) since I feel that will be more important to hash out at first (you don't want 5 people wanting to tank when you only need 3 most of the time, for example)
Of course, a lot of this will depend on who is available and ready to raid, at least for the initial phases since I feel many guilds will be in a "take who is available" mindset to begin with unless they are highly experienced with 40-man raids and have a large stable of players ready, but I'd like to at least get some basic ideas down to share so we know for recruitment purposes what we might look for.
I'm having trouble finding resources that discuss this; most seem to not mention a role breakdown at all except for very specific fights.
Protecting the weak, punishing the wicked
This is purely from my memory raiding 14 years ago, so I'm sure someone from a pserver will correct me on the current meta: it's also from the perspective of seeking to progress while accepting that you aren't going to get world / server ifrsts.
In general your raid composition will be dictated by who is online for raid night. Getting 40+ people online and ready to raid is a herculean task. Your recruitment (which you should generally be constantly doing) will focus towards fleshing out what classes you aren't routinely bringing, so your 'optimal' raid comp is going to be a reflection of your guild composition for the most part.
In general, tho:
Tanks: MT + 1-2 dedicated OT + up to 5 more people capable of tanking. You're going to be relying on warriors for these spots but the goal is to bring DPS that can also tank for select fights. And yes, feral druids are good here if they're very capable. Not all these tanks need to be warriors, but realistically none of them are going to be paladins (particularly true if you're rolling horde, lol)
Healers: 6-10 (2 on MT, +2-8 flexible assignments as per boss). Generally 6 healers would be the absolute minimum I'd be comfortable with and 10 would be too many for most fights, so they'd weave in DPS. On some tank & spank fights the healing is very straightforward: other times you'll need specific healing assignments for every group, so it pays to have 8 healers in the raid to make that simple and efficient.
This is the bit I'm the least confident about. In the olden days no one had any idea what they were doing so people brought a LOT of healers.
The rest of your raid is DPS, so that means 27 DPS of various flavors. Things people do to optimize: you don't need any of this but it's always nice.
Warriors to swing Nightfall / that other debuff axe
Shadow Priest for Shadow Weaving (If you have a goodly quantity of warlocks)
1 Feral druid for melee dps aura
Warlock in MT's group for Imp Stamina buff
1 Hunter for Trueshot aura
Enough paladins and shamans to cover key groups with essential blessings / totems, windfury and kings/wisdom being the big ones
For a long time we had too few healers, then towards the end before BC we had too many. I would say you'll have no shortage of DPS for sure, but quality tanks are precious and you should do whatever it takes to keep them happy.
TL;DR: MT, 1-5 OT/DPS, 6-10 Heals, rest DPS.
I say this as a warlock main. Don't bring a shadow priest if you want to optimize raid set up. They increase warlock dps by a good amount but they do so por dps themselves that it is not worth it. What always is worth it though is to have one healing priest spec in to shadow weaving to get the buff, focus on healing and just keeping the buff up with rank1 shadow word pain. I do think ret paladins are valid as a nightfall swinger, this is only if you already have enough healers but not all the Pala buffs you want. This has a lot to do with filling the rolls you need with the people available, warriors are great but the lose so much dps themselves being a nightfall swinger, paladins don't but they also don't do that good damage to begin with so it mostly comes down to the people you have available there.
It depends on what phase we are on and what classes you have at your disposal. Certain classes like hunter are incredibly valuable during phase 1 and then slowly drop off.
A typical raid comp would look something like this:
Depending on if you are horde or alliance this will change. Also depending on your comp and top performers this may change... For example, your best 4 players are warlocks, you may want to take an additional 2-4 locks and have one of your hunters wield nightfall and one of your priests to go shadow to ramp up their damage. Similarly, your warlocks might be utter trash and you may be having more success with your melee team, so you may need to emphasize their success.
These numbers also have lenience for the odd meme spec to join the party. Add a competent feral druid into the mix to round your raid up to 3 druids, etc.
These raid comps will always vary slightly between guilds and attendance. I would always start MC with a strong hunter core to carry the raid, acknowledging that player attrition will slowly weed most of your raid out anyways. Then as your guild begins to progress through tiers 1 and 2, begin to place an emphasis on recruiting classes that will shine in AQ40 and Naxx.
As far as the specifics of healers will go, this will be dynamic. You will start with more than you need and weed out the poor performers. As you prune the healers that arent needed, the ones you do need will become more engaged and more geared. Those replaced will allow you to add additional DPS and increase your raids overall throughput. There is no template for the perfect raid. General guidelines should be followed and you should mold your team to succeed as you progress.
Role composition varies somewhat by tier (Phase in the case of Classic)
Tanks + Off-tanks go up as you move from T1 (2-3) to T2 (3-4) to T2.5 (4-6 depending on encounter) to T3 (4-8 depending on encounter)
This counts both dedicated MTs and OTs (either ferals or dps warriors that keep a tanking kit relatively updated)
Healers also vary but in their case it has more to do with performance upgrades for the rest of the raid (both in terms of gear + coordination)
Healers "lose" their spots to DPS the easiest the content becomes through either of the above.
I'd consider 6 heals very low for a full 40man roster assuming a raid that is progressing or farming a zone (and not going back to MC for bindings with 2 tiers higher gear)
In my experience 8-12 is a more realistic range (and yes I realize that spread is huge)
A lot of these are skewed drastically from private servers (tuning accuracy and combat mechanics on high level content pending verification, the unprotected Lua API, buff meta etc) and a specific kind of (speedrunning) guild.
Expect things to hover around a 4/11/25 role split with variations by encounter, tier and progression/farm status.
It will not be much different to what top guilds in 2006 used.