Throughout the life of WoW (or MMOs in general I suppose), there has always been a trackable rise and fall in guild participation over the course of a year - especially as pertaining to 'progression' raiding. When the BC release date was set, and the battlegrounds saw a major overhaul to the ranking system, raiding all but ceased. Why spend hours every night breaking your skull on super hard bosses when you could get a fair share of gear in less time by PvPing?
School, work, summer, and vacations all take thier toll on raid participation. When you add in the frustration, or lack therein, of difficult content - it's quite easy to lose some of your raiders. Regardless of thier role, losing a seasoned raider is never an easy thing, and there are always challenges with replacing them.
So long, and thanks for all the fish
How you lose members reflects greatly on both the members, and the guild as a whole. Recently (like within the last 48 hours) we lost our Warrior tank and his Mage GF. Both handled their removal well, sending a PM to the officers stating that they were going to step down from 25 man raiding, and focus on the 10 man stuff. A little bigger heads up would have been nice, especially since there is the expectation (on their part) that they would remain in the guild. In the end though, it's their decision to raid or not, and I'd rather have folks in the raid who truly want to be there.
In all honesty, nobody was caught off guard by this move, which makes it slightly easier to deal with. When they joined the guild they had originally stated that 10 mans were their preference, and they pretty much raided 25s with us so they could see the content. Plus, they joined with a few friends who have either quit raiding, or been demoted due to attendance/perfromance issues.
A different type of flow
With summer on us, we'll probably see a slight drop as folks go on holiday or attend family functions. I know I've got three weddings and four races to attend this summer. Depending on the dates, that's up to seven raids I might miss. School will start again, and the college kids will disappear for a few weeks until they get a handle on school. Holiday breaks will see another dip, and so the cycle will continue.
In BC there was the flow of participation as guilds that had TKE and SSC on farm waited for BT, and again for Sunwell. This isn't a huge impact on guilds that aren't on the bleeding edge of content, except that you lose members going up to higher guilds that suddenly have openings. When Wrath was set, and 3.0 nerfs rolled over the land, guilds that had already been gutted scrambled to fill thier ranks for Wrath raiding. The time was perfect to get yourself set in a new guild, ready to push into Naxx and beyond.
The Naxx Bomb
Naxx failed to deliver real raid content from the moment it was released. It didn't help that Ensidia et al. cleared it in 48 hours or so. PUGs were downing KT in a week, and you can't run the LFG channel for 10 minutes without seeing some sort of Naxx come up.
Where Naxx really failed, and yet was at the same time insanely successfull, was that it failed to teach raiding skills. AoE was the order of the day, and facerolling could get you through most of the encounters. Lost were the skills of chain sheeping, saps, and overall CC and tank positioning. Now we've got hard modes that are truly hard, and the everlasting challenge of not standing in Sara's green gas. Guilds are breaking against the rocks of Ulduar, and the shakeup has begun again.
S-a-S is positioned nicely, in that it's always easier to recruit if you're on the top of the food chain. Our biggest challenge will be finding members that mesh well, and getting them geared to handle the hard mode encounters. Hopefully we'll keep rolling over content - but only time will tell.