We recognize that, for some guilds, the transition from 10-player Heroic raiding to 20-player Mythic raiding is going to be something of a challenge. This wasn’t a decision we made lightly. Ultimately, we feel that the long-term benefits for everyone, such as better-tuned raid encounters, a faster encounter design process, and more variety in raid mechanics, are worth the short-term consequences – even for players in guilds facing this transition.
That said, I think there are several key factors worth bringing up that will help make the transition less frightening overall. For example:
1) This change is coming with an expansion. Historically, an expansion release has always been a volatile time for guild rosters – and a great time for recruitment. When everyone’s gear is suddenly equalized, the pool of potential recruits swells dramatically. It's also a time in which a lot of former players, friends, and guildmates return to the game. Sure, maybe not all of the above will be of the caliber you’re looking for as a Mythic-minded raiding guild, but you only need 10.
2) On a similar note, we’re continuing to roll out the Connected Realms feature. As more realms are connected, the potential recruitment pool on those realms will grow.
3) While 10-player guilds who want to do Mythic will need to pick up an extra 10 people, current 25-player guilds will need to shed some. That’s yet another thing that will lead into a higher pool of potential recruits.
4) Flexible scaling for Heroic (or Mists of Pandaria's "Normal") difficulty will allow many guilds to "ease in" to a 20-player raid size. Granted, if you’re planning on zoning into Mythic the first day it’s available, this won’t help you much, but for the guild that will spend a few weeks or months on Heroic (MoP Normal) difficulty before eventually clearing it and starting on Mythic, you’ll have plenty of time to expand your roster. What’s more, those new recruits won’t be expected to just warm the bench while they wait.
I think that’s an easy one to forget about. It’s easy to make a mental comparison between a Warlords of Draenor 10-player guild trying to recruit up to 20 for Mythic, and a Mists of Pandaria 10-player guild trying to recruit up to 25. But that comparison doesn’t really work, because the absolute biggest challenge that the MoP guild in this example faces is finding people who are willing to wait around and possibly not even raid as the guild expands its roster. That’s not a problem in Warlords – while you’re still working through and gearing up in Heroic, player 11, 12, 13, and so on will be able to join you. It’s much easier to keep recruits around when they’re actually getting to play. :)
Seeing a lot of debate about the number 20. Let me take a stab at clearing up a few things:
We chose to put Mythic at 20 largely for the function of raid design. One of the biggest issues we're currently facing with 10-player Heroic raiding is that of raid composition. It's impossible for every group to have every class, and often that means they're lacking in certain tools, which in turn means that we can't design encounters around those tools (or if we do, it becomes extremely frustrating for the 10-player Heroic guild that suddenly needs a Paladin for Hand of Protection).
We want to be able to use those sorts of mechanics again. Those of you who have been with us for a while might remember things like Mage tanks on High King Maulgar, or Priests using Mind Control on Instructor Razuvious. We want it to be okay when, say, the Paladin can use Hand of Protection to clear a dangerous debuff, because we can reasonably assume that most guilds will have at least one Paladin in their raid. We like it when someone gets to feel awesome and have a special task on a fight because of class abilities that otherwise wouldn't get much use.
We can't do that when we're designing with a 10-player raid size in mind. We don't think we'd be able to get away with it at 15 either. At 20, it becomes a lot more acceptable for us to say "you should probably bring a Mage to Spellsteal this." And honestly, that's just one example of the sort of encounter mechanics we can start to utilize in a larger group size.
I'd also call into question the statement of "It's easier to drop people than it is to recruit them." It's technically true, yes -- finding new raiders is harder than just not inviting the ones you have -- but totally ignores the fact that cutting people from your roster often means losing people you like. Which feels better: making new friends, or telling your current ones that they don't get to play with you any more? We're already asking a lot of many 25-player Heroic groups to cut 5 people.
As I mentioned before, this was not a decision we came to lightly. It's definitely going to be a very scary transition for a lot of people. We knew that when we made the decision. We just also feel quite strongly that, when the dust settles, we'll be able to provide a better raiding experience for everyone.