I think it needs to be said, if you are posting the LFM and intend on booting and squelching anyone who dares show up in a destiny they're trying to level.
I've done lots of EE runs where no one cared what destiny anyone else was in, and we still had fun and still completed. I've also seen LFM's that specify everyone is supposed to be in their "best" destiny.
It makes far more sense to specify in your LFM than it does to just assume that everyone will "know" they have to be in their "best" ED and that they will be booted and squelched if they aren't.
Listing requirement in the LFM helps of course, and it depends on what content we're talking about, nobody probably minds if you show up in a weak destiny for EE Impossible Demands. I believe OP was referring to harder quests and raids where everybody actually needs to be able to contribute.