The reason why dungeons have been boring these last few years are a combination of two things. The amount we get and they all use the same formula, kinda like if an amusement park had a bunch of roller coasters that was all the same except the paint and some random things on the side, still the same roller coaster even if one has an elephant on the side and one has a panda.
The right way to deal with dungeons, and as a result the expert roulette, being boring is not to add less dungeons, the solution is to change the formula.

But how can they change the formula?
A dungeons does not need to be 3 bosses, it can have everything from 0 - however many they want. How to deal with the loot? Just throw it all in at the end.
A dungeon can have traps.
A dungeon can have exploration, even if it is just the illusion of it.
A dungeon can have hidden bosses.
A dungeon can have parts that are randomly generated.
There are so many things that can be done here, but I guess reducing the amount is cheaper and frees up resources for single player story related content that we will only play once.