The most difficult boss of every MMORPG guild is the roster boss, the boss that never goes away. Raids in most games have strict group numbers in mind, meaning you need exactly X number of players in the raid for the best time. You can run with less than that number, but it will be less optimal except in rare cases.
The tight specification is what is very difficult for many raiding guilds to handle. In professional sports. there are bench members who replace starting players that swap out for various reasons. In real life, there are several reasons why players are swapped out, from injury, fatigue, penalties, and more. However in the video game world, there are a lot fewer reasons to need to sit out. There are certainly times where work, personal life, health, or other reasons would cause a player to miss out on raids. In practice, most raiders are consistent in their attendance and rarely are raiders swapped out mid-raid.
While swapping out raiders mid-raid is possible, especially if encounters call for different compositions or if a particular piece of loot is more sought after, what happens in practice is that players play for the whole raid and those who are on the bench find a different raid to attend. This places players in a strange spot of not truly desiring to be on the bench, as there is no salary and no guarantee of any progress without physically being inside of the raid instance.
A lot of guilds build their guild size to be specifically the raid size plus 10-20%, allowing their players some variance in attendance and pulling from the more flexible players when needed. The common problem with this solution is that the window for this opportunity is quite small, as losing a few members opens up the doors to key positions being unfulfilled. Guilds in this position attempt to keep equilibrium by constantly recruiting and maintaining the current playerbase.
Another approach is to spill the group size over into a second or third raid, filling the raids with alternate characters and more flexible players. Alternate characters are great for filling raids because the players that pilot these characters already have experience and some are willing to take lower priority on items or attendance in favor of allowing more unique raiders in their guild the chance to raid. The difficulties in this approach are requiring multiple raid leaders and raid times, as well as a community that is robust enough to support multiple raids or identities. Common problems with this solution is lack of organization or leadership and lack of opportunities for players to engage how they would like to. If it becomes clear to players that there is a distinct difference in quality or availability, players will naturally dissolve and dissipate to other guilds.
The solution to my particular guilds problems will be to adopt and adapt a second approach, while finding guilds in the former approach. My current raid roster is a bit weak, despite my guild reaching the guild limit of 1000 members. There is a lot to processes to move forward, such as leveling members hitting 80 and level 80 members getting raid ready. To accommodate so many different players, attitudes, and schedules, my approach is to find outlets and multiple avenues, networking with other leaders so that instead of our groups competing with each other and losing to the roster boss, we work together and preemptively tackle content as a collaboration. Many guilds lack an identity outside of raiding, outside of their core attendance. It is possible we can provide a meaning to these guilds, to the few players who desire more than just raiding. Networking opportunities with other guilds and raid leaders grants us the powers to handle the roster boss.