Having to clear trash otw to bosses will probably never go away.
But maybe give players more options in the dungeons, instead of just running in a straight path, with a few off to the side rooms with chests?

Sorta like how they did with 1.0 Toto-Rak... You could go for all bosses or just 1, decided how many chests would actually pop at the end.
https://www.youtube.com/watch?v=RETh2jSXEQs

Heck, 1.0 Tam-tara was a HUGE dungeon aswell, with many different paths.
https://www.youtube.com/watch?v=eLJPTUG-dE0

Maybe dungeons like this could help? Remove the timer on the dungeon and let players choose just how much of it they wish to do and spend time on.
So if a party simply want XP, they could spend the time needed to clear everything.
But if others just wanted boss loot, they could just clear trash directly to the boss as its currently happening in dungeons.

And please SE... 2 years and 1 expansion later, and we are still listening to the same damn battle music in all the old dungeons... Why cant we have the full music tracks back again please?