The eternal matchmaking is a good addition to the game, but one thing is a huge problem now.
Many higher level eternal dungeons need good planning ALSO in terms of specific TRINKET choices AND TALENT choices. These can't be changed when "match has been found" so it kind of makes the matchmaking system pointless in the higher tiers.
There should be some kind of "lobby" for the matchmade team to switch gear/talents after which people confirm again to start the match.