Move the 100 myth message to the end of battle or get rid of it
All this message does is promote harassment and exclusion of new players. As it stands now, you can practice practice practice the battle all you want, but at some point you will have to join a farming PT to get the clear and unlock new content. But oh wait all the farming parties have "NO 100 MYTH" in their PF comments.
"Just get a static!" I hear the apologists shout. Some people can't play as much as they'd like. Are they banished to farming last patch's content forever? Is that really fair?
Is this the devs' intention? Designing a team jump rope game where if one player F's up, everyone dies? Creating a toxic community?
The incentive is too weak.
I personally don't really care for 100 myth. You are not doing these fights for Myth, you want the loot at the end.
One thing that would absolutely give most people the incentive to teach or take on someone that has not cleared would be to have this bonus of 100 myth(soldiery in 2.4 most likely) replaced with "greatly increased drop rate of items" such as mounts, mirrors, Ramuh weapons those items that don't drop 100% of the time and also the craft items for bardings and furnishings.
Also for fights that do not have additional loot that don't always drop, like Coil for example. For Coil you could have the chance for additional armor drops from chests.
This is such a simple solution and it's only a "chance" you can't exploit it and most of all, everyone will want the bonus that the person that hasn't cleared gives you.