One of the things I find frustrating about trying to do some content is that it can be hard to simultaneously get the right group on and find the mob up. This game should be about beating the strat of the mob, not about obsessive tracking. Imagine how fun it could be to able to just tell your friends, "hey, we are going to do Mountain King tomorrow at 5" and be able to. Imagine how easy it would be to get people to log in on raid night if they KNEW the super-fun fight everyone wants to finally beat will be up.
Given that, what would I like to see? Raid content with very short respawn timers that don't allow any particular player to kill it more than once per...however long...3 weeks? If you are loot eligible when it dies, you get flagged and denied re-engaging for 2-3 weeks, but it will repsawn quickly (<1 day) for the next group to try. Hardcore players can't farm it up quickly; casual players are not denied experiencing the content.