I'm on a server with a total of three level 50 players. I queue with one of them, but we don't have the option of forming groups.

We've found that queueing for Amdapor Keep is better than Wandering Palace, because the unskilled legacy players are unable to unlock it. Either way, it's kind of a silly problem.
I was under the impression that champions like Garuda, which are very punishing of single mistakes, were to gate these players off.

The issue is primarily that in order to reach level 50 from scratch, in 2.0, you need to have a good understanding of your class and game mechanics, which comes from various story quests and guildhests. These players completely skipped that. It's almost akin to giving a brand new player level 50 and throwing them into the game. I'm not sure how anyone can defend this.