One of the primary struggles I face in a guild with no attendance policy is getting warm bodies to fill 25 raid slots for every raid. It seems like it doesn't matter how many people we recruit these days, we just can't seem to get enough people to make it happen all the time. As new players join us, old ones get burned out or stop playing altogether to wait for the next expansion. Based on this, you might already conclude that I can't really help the person who wrote this week's e-mail -- and maybe I can't! But I've learned that sometimes other factors can come into play, and this person might already be onto one of them.
I am in a raiding guild that usually runs about 3-4 raids a week and currently we are progressing through Black Temple as we have already cleared Mount Hyjal. [. . .] Recently we have had some issues with people showing up to raids and it seems to coincide with when our guild leader (raid leader) is not able to make it to the raid. If our raid leader doesn't log on we can't seem to fill out a 25 man raid but when he does log on we have no problem. Not really sure why this phenomenom happens but it seems to happen every time.
Neur, never underestimate the value of a good raid leader. I highly doubt it's a coincidence that you have more people showing up for the same raids your primary RL attends. Have you noticed that raids tend to go smoother when he or she is leading them? Are there more boss attempts in less time? Are most of your guild firsts a result of his or her leadership? When he or she isn't there, have you noticed that everything just seems to drag a little bit?
If you're answering yes to these questions, then you have your explanation. Raiders, particularly raiders with the experience and skill to progress through Black Temple, are quite adept at noticing patterns. It sounds like your members have picked up on this pattern and are attending accordingly. They've giving themselves what they feel will be the best chance of success in the least amount of time.
If you're answering no, then maybe the problem is of a more personal nature. Maybe some of your members just flat out dislike the person who leads the raids in your RL's absence. Have some private conversations and see if anyone has a problem with the "substitute" RL. If that turns out to be the case, you might have to mediate discussions and help the members involved to see eye-to-eye again -- or at least get them to the point where they can stand to see each in the same raiding window. You might even have to find someone else to lead the raiding team or, as a worst case scenario, base your entire raiding schedule on when your primary RL can be there. But hey, worse things have happened.
The beginning of summer and the launch of new MMOs are always, in my experience, the nadirs of my guild's attendance cycle. I expected a nasty dip this summer, with the convergence of the two events this year in addition to the gap in content for WoW. So you're right about those things. However, since there's a definite link between overall attendance and this particular person, you need to figure out the connection in order to find the solution.