Seriously fix this now, its ridiculous that this is even a thing. Should not even be able to join legend at level 1. Let alone host it
I think the only requirement for Legend is some amount of hero power, which evidently can be met with 300 power gear alone.
As for the other thing, they know about it and will hopefully come up with a solution soon.
If anyone who isn’t planning on actually playing would like to counteract this behavior, you could do the community a favor by entering the troll lobbies and just staying in them. Any character slot you take up in their lobbies is one less chance for them to troll people.
Start the game, find their lobbies, hang out in them as long as they’re up, and read a book or browse Reddit or listen to a podcast or whatever. No insults or interaction with them needed, just passive denial of their ability to troll people.