Over at WorldofMatticus.com, there's a poll going for who's planning to do 10s or 25s come Cata. The verdict is in: lots of players want 10 man raids, and many players are calling this the death of 25s. In game, there's almost a venom that comes out with this discussion, as if there's a horde of players who have secretly hated 25 man raids and can't wait for them to writhe in a horribly-fiery-painful death.
However, there are a few advantages of 25s that I haven't seen discussed too much. I'm glad that there are a lot of players excited about the change to lockouts (it means that Blizzard made the right choice, and that lots of players are doing 25s when they don't want to). But I don't believe that 25 man raids will die, especially not by fire. There are advantages that larger guilds have in terms of logistics.
1. Maintaining extras in a 25 man roster is easier than 10 man. All raiding guilds want to have at least a couple of extra damage dealers and healers hanging out in the wings. So the guild over-stocks itself, knowing that every raid night, a couple of folks won't make it, and a couple will be benched. It's expected that in a healthy 25 man guild, there's a wait list (perhaps not over this past summer or fall, but, you know). In this case, you have anywhere from 7 to 14% (3 or 4 of 29) of your raid group sitting out each week. Ideally. Odds are, in a 25 setting, it would be less because the larger the group, the more likely there's a meeting/school event/birthday that keeps a raider away.
In a 10 man group, ideally, you still want to overstock but the line between too few and too many is less clear. Suddenly 12-25% (3 of 13) of your raid force is going to be sitting on a given night, if everyone showed (which grows more likely with a smaller group). If your main tank doesn't show, it could spell a cancellation. In a 25 man raiding guild, there's more likely to be someone who can switch specs for the night or be brought in.
2. 10 mans rely a lot more on 100% raider attendance. How many 25 man raids have you done in the past few months, shy a damage dealer or two? Or, even with the most borked raid comp you could think of? I can think of plenty times we've gone and done the easy bosses with 20. Hell, we've progressed with 24.
Try that in 10 man? There's achievements for that, but I doubt it's a healthy thing to try to do new bosses that way, and not consistently. Especially if healer mana is as constrained as predicted, doing a fight shy one raider on 10 man is a risky endeavor that will punish the healers the most. Culling a damage dealer prolongs the fight, dropping a healer could push remaining healers too much.
3. 10 man raids will be tuned for the same gear level and be harder. For the first two tiers of content in Wrath, I never did 25s, and I found 10s to be pretty hard at gear level. I think the strict 10 man progression raiders would agree, too, if you don't outgear the instance, 10s aren't exactly faceroll now. I never did ICC 10 without severely overgearing it. Period. I came in with 245 gear, when it was tuned for 232 gear. That's a big difference in spell power, luxury stats like haste and crit, and blue bar. That's extra gem slots, too! I'll admit, I have no idea what 10 man progression in Icecrown should have felt like, because I was already geared with 25 man ToC gear.
If 10s are being tuned without the lower gear requirement, a lot of players might find 10s harder than anticipated, especially since each player is 10% of the equation, as opposed 4% in a 25.
4. 10 man and 25 man often have different loot systems. I'm a huge fan of EPGP. I think it's pretty darn fair (I'm biased, as a player with 100% attendance who only takes what she needs). Since I do 25s and that's where my "best" upgrades come from, I could care less when I lose a /roll in a 10.
I suppose this statement relies soundly on a few assumptions. Most 10 man runs I've ever seen do a /roll, often limited what you can main spec per wing/per boss. I haven't heard of many 10 man guilds that have a formal loot system, and I have a hard time picturing how something like EPGP or DKP would work. I don't have any experience with loot council, but any system that favors attendance over a /roll is going to put the players is going to put the casual folks recruited to be available when you're short at a severe disadvantage.
ESPECIALLY if there's less loot per boss on 10. That could get nasty. In a 25 man, a casual member just helping out for the night still might walk away with some upgrades despite an attendance system (more drops per boss, the sooner stuff gets sharded/goes to offspec). In a 10 man, it seems less likely, especially if the 10 man is designed to "gear players up" more slowly than 25 mans, then more of your players are still waiting on specific upgrades. The regular raiders would be hurt by a /roll, but the casual would have no incentive to join if they have to pass to the regular raider.
Less loot in 10s also exacerbates the recruitment issue. Less gear going to offspecs could limit your raid's flexibility. It's been easy in Wrath to maintain a viable offspec (how many druids and paladins do you know that have three sets of gear?), because with the dailies, badges from two lockouts AND two/three weeklies, and drops from two lockouts, the gear is out there. In Cata, we'll only get one lockout, and we'll be capped on how many PVE points we can get in a week.
If 10 mans are designed to take more time to gear up, that further delays the drops going to off spec, limiting how many folks are going to be able to switch as needed. Players who value their flexibility may have incentive to do 25 man raids. I imagine that even 10 man raiders will be able to keep offsets, but they might have to mix and match some lower tier gear to do it.
While it's true that healers and casters maybe be able to use a lot of their main gear for their offspec, that doesn't help tanks, paladins, or enhancement shamans. Their offsets will be built from scratch.
5. 25 man raids, in Cata, can shift down to smaller raid sizes on short nights, while 10 man groups can not shift up. A low attendance night won't cancel the larger raid, assuming there's enough tanks and healers, as they can at least do a fight or two at the 10 man size.
6. Problem players and cliques can claim more authority in a 10 man raiding group. Lots of players like 10 mans for the intimacy (I do, too). I have accepted that in a 25 man environment, there will be at least a couple of absolute dicks. If I choose to progress in only 10 mans, I wouldn't put up with even one. I'd want to genuinely like and respect everyone in my 10 man group, while it's expected that in a larger group that just won't happen. Personalities meshing in smaller groups is more pivotal for group success than in larger raids.
Smaller groups can potentially be polarized by issues and personalities. Just like the difference in feel between a small business and a corporation, the comfort and intimacy can become a liability if not carefully handled. In that respect, 25 man guilds can promote emotional distance and professionality, which some players look for in their raiding environment.
Don't get me wrong, I'm not trying to suggest that 25 man raids are less likely to get emotional or have drama explosions, because that's not true at all! What I am trying to say is that it rocks the world of a 10 man guild when 10% or 20% of your raiding force ragequits. That's the potential to call the raid for the night, which is quite a bit of power in the hands of one individual. In a 25 man raiding guild, the individual holds less power and therefore can't emotionally blackmail the group. Granted, these aren't the players you want in your raid anyways, but calling a raid early for a night or not raiding at all is dangerous for guild morale. I've always felt there was a higher potential for fallout in a 10 man group over the 25. It's more intimidating to risk pissing off 24 people than 9.
6. 10 man healers will (likely) be less specialized. This is quite a bit of speculation on my part, but I predict that Blizzard's motto for healers of using the whole toolkit will come out much more in 10 man raids than in 25's. In larger groups, there is more room for specialization, while in small groups there is a need for versatility. Healers who want to specialize could very well be happier in 25 man raiding group, especially healers who expect to be doing the same job all the time. That isn't to say that tank healers will never cast raid heals or vice versa, but I predict that I want to define myself as a tank healer, I'll need to stick to 25 man raids to do it. In a larger group, it's easier to specialize and expect to fulfill that role. A lot of healers will love the versatility of healing in 10 man raids (I like playing my priest and druid more in 10s than 25s) but some will still prefer to specialize.
7. Managing a 10 man really isn't that much "easier" than managing a 25, it's a busy job no matter the group size. I've done both, and obviously YMMV, but personally I've found being an officer in 25 to be simpler even if the volume of tells is always worse. With a larger team of officers, my role was clearly delineated and there was almost always another officer online to confirm policy or ask for support. Going back to the small business analogy, a 10 man officer is going to juggle more hats. The 25 man officer is going to take care of the assignments given to them, and deflect other matters to the correct officer. Established roles make for less stress and less stepping on toes.
If I were offered a leadership position again, I'd rather take it in a 25 man guild than a 10. The argument that no one will want to manage 25s falls flat for me. It's a lot of work and emotional investment to manage a guild, no matter its size.
TL;DR: If Blizzard stays true to their design mission of play the raid lockout you WANT to play, I believe 10 man raids will be a lot more prevalent, but I don't think it's the death knell for 25 man groups. There will still be incentives to do the larger raiding groups, and I think there will be enough players who genuinely want to do 25 mans to do them.
I have yet to see what raiding will be like in Cataclysm, but I have a good feeling I'll be playing with the folks I want to raid with, whatever lockout that ends up being. I voted "banana".
LICH KING UPDATE: I KILLED 25 LK LAST NIGHT, and completed 7 hardmodes this week! (My guild is up to 8 hardmodes, but my internet sucks so I had to step out for Saurfang, which really bummed me out.) BUTBUT shiny new mace and I just broke 43,000 mana!