Last week I put up an archive post considering raid-number-crunching. That post was made during cataclysm, but look, we gained Monks, so let's do it again.
I am using several basic things here. First up is raid spots. In a 25 man raiding guild with 3 nights of raiding you will have 75 raid slots per week. Now if you add a required attendance of 67% (two-thirds), you'll find that you actually need 37.5 raiders to fill all slots. If all those 37.5 raiders raid twice a week, they will take up 37.5 times 2 is 75 raidslots.
Now we have different roles, so I also will take those apart. And I will listen to "Bring the player, not the Class" so no class will be favored because they may just be the flavor of the month. Although some nice gimmicks may help (looking at warlock portals)
Every raid needs 2 tanks at least, raiding through Throne of Thunder, I noticed a lot of fights where three tanks where actually more helpful, and actually 25-raids should need 3 tanks (imho). So if we go with 3 tanks for 3 raids, we get 9 tank-slots. 9/2=4.5 tanks needed. Now if you have a lot of turnover, or tanks actually only raiding twice a week, then maybe you should go for 5, but I'll take the number 4, because not all fights need 3 tanks, and some dps can step in probably. So; 4 Tanks
But which classes? Well, we have three plate-tanks, and two leather tanks. Two classes which use a Shield, the leather classes in the same pool as the leather-dps, so gear to divide among more. I would say at least 2 plate-tanks, and 1 leather-tank, fourth can be anything I guess, now if I would have gone for 5 tanks, it would have been easier...mmm.
"Every raid needs 5-6 healers, and on hard fights 7" -end quote. So let's go with 6 I assume, and again looking back at the last tiers, six seems to be the number. Throw the number 6 into the equation, and you get 6 times 3 divided by 2 is 9 Healers. Seems a little bit low, but again, a dps might jump in I guess, for now, let's go with 9 Healers
So, which classes? Let's look at gear, monks and druids share the same gear, the rest of the healers dip in other stuff. So two of each healer, except for monks and druids, which together should be 3, thus making it 9.
So basically, what is left are the DPS, so 37.5 minus 4 minus 9 makes 24.5. I will up the number to 25 here, probably because it always feels DPS have a higher turnover. So 25 DPS
Now it gets more interesting, if we go with 2 for each class, we end up with 22, missing 2.5. If we consider that 4 classes cannot be healers or tanks, the so-called 'pure' classes, we may add 1 each for those to even the score a bit (and also looking at tier-tokens). So, we end up with 26 DPS. Which is one to high... luckily we can easily drop a rogue because they deserve to...well, more because melee always seems to get the problems in raids, and I had to exclude some-one.
So, a 'Perfect Guild' would have the following composition:
1 Warrior, 1 Death Knight, 1 Monk, 1 Paladin, 1 Druid (One Tank designated as Main-dps/OT)
2 Paladin, 2 Priest, 2 Shaman, 3 Monk+Druid
3 Mages, 3 Warlocks, 3 Hunters, 2 Rogues, 2 Shamans, 2 Druids, 2 Monks, 2 Priest, 2 Paladin, 2 Death Knight, 2 Warriors
Because the quality of the raider is more important then the class, this is not written in stone, although a 4/9/25 dividing is probably a good template, that all depends on the availability of different players in your guild.
If you have more healers with uncertainty, you could go for 4/10/24 for example.
Now, to actually let these numbers loose on Innovation, but that will be another post....
And there is also another aspect, which I may hit up on next...