I've seen this "elite mobs areas for parties" in a lot of MMORPG, I've seen both MSQ and sidequest tied to them.
There's usually no problem at launch or during the first months of the content, since well of course, that content is new...

The problem starts when time passes and content becomes obsolete, either because you only need to run it once (MSQ, once & only sidequest rewards, etc) or the rewards become outdated. What happens to the late comer then? they get stuck waiting for other late comer, or someone who wants to help them run content which won't reward them.

Few things suck more than getting stuck in a MSQ because you have to "get to X item and activate it" in an area packed with elite mobs with no way to avoid aggro in it, and no one helping because it's a dead zone/content.