Even if our server isn't small (and I disagree), it's still shrinking. Now I'm well aware that the expansion with inject it with new life, but I think the point of the OP is that there are steps that can (and should) be taken to make the experience as close to optimal for as many players as possible. Regards of what specific niche people fall into, the fact still remains that actual combat content is necessary for a great many things. If after we consistently tell people they need to get certain abilities from cross-class, or give advice on things that need to be done and they don't listen, they get written off as bad. I'm guilty of writing people off.
You are most definitely right about end-game being small. Many people who can actually complete said content and lead people to victory insist that they are bored, and when challenged to help insist on staying bored. If however we are able to to expand the number of people able to do they activities, our options will grow. I also seriously doubt that <10% of the server is interested in FCoB. The fact remains that it is content and so people want to do. Sadly, some people are stuck on t5. Others t9. As such they don't have access FCoB. If after we consistently tell people they need to get certain abilities from cross-class, or give advice on things that need to be done and they don't listen, they get written off as bad. I'm guilty of writing people off. However, I'm also open to the idea of improvement. Very rarely will a random listen to advice from strangers. At that point, it's the FC lead (or supervising agent) who needs to show they the right path.
My point is that to increase the size of end-game challenges tackled on a daily basis, we need to increase the number of competent players. We don't need to be harsh, just truthful. I kicked a whm from 11 for consistently wiping us, rather than disband the party. A few days later, the whm told me she'd improved and you know what? She had. We wiped and the sch tried blaming the whm because of her history, but the whm was pretty close to flawless. It was the sch who murdered us. The whm, on the other hand, had accepted her short-comings and worked to overcome them
Almost everyone who plays this game is over 18. Sure there are lots of people who are under 18 but really, there's no reason to coddle the average player. We are adults. Teach us what we need to know and we can make progress. However, the most important thing is to be truthful to those closest to you. When you know your colleagues aren't performing as well as they should be, but insist they are doing well, they tend to disregard the wisdom of an outsider.