This Needs to Be Said

[Reynhart]

The community would find the most efficient way to clear content and follow it only, effectively making anything else in the dungeon a waste of development time.

You're right about that, but it doesn't change the fact that dungeons are easy to make. As for the scenery, most dungeons only reuse existing textures from the real zones. And most monsters also reuse past 3D models, with a different texture sticked on it.
Besides, before we had content like Diadem and Eureka, we still only one had "new" dungeon per major patch, the others were only reusing past maps and assets..and we still have our "new" dungeon each patch.

Yeah, sadly, non linear dungeons don't work very well in practice. Blizzard tried many, times.

I wouldn't say that, and more "branching path that offers nothing don't work well". I think they could have a dungeon where you can do the first bosses in any order you want, and once you've killed the three of them, then the final room opens for the fourth boss.
Funny thing, Toto-Rak was much more interesting in 1.x, where the numbers of portals you activated actually changed the location and the strength of the last boss. You also had additionnal rewards at the end for opening every chest, encouraging you to explore the branching paths. 1.x Cutter's Cry also required you to split your party in two because you had to clear rooms at the same time.

Set it up so that it only pops up when you go in there.

When reading this, what comes to my mind is the Achievement pop-up you have when you zone, and I tend to ignore it every time