One thing I tend to notice is that some raids have a ton of trash either at the start (like EP) or in the middle (Uldir) but have hardly any towards the end.
Uldir, BoD and EP have no trash between the penultimate and ultimate bosses. And Ny’alotha is the same. Hell you finish the Carapace fight IN N’zoths boss area. I don’t think blizzard has ever done that before to my knowledge. Excluding ToC of course as you fight 4 bosses within the same area anyway.
Side Note: I would also include Hellfire Assault and Iron Reaver in my exclusion list, as the two are kind of a single boss encounter split into 2 parts. Like Spine & Madness, alongside Carapace and N’zoth. Since Mar’tak is in Hellfire Assault, and she pilots the Iron Reaver to stop us from entering the place after blowing up the gates. So it makes sense to use the same boss area for both encounters from a narrative point of view.
I think this is because you tend to have options on which boss orders you want to go. So blizzard inflates the amount of trash between each “boss” so there is no true “quick” way to clear to the bosses. Especially if you got a situation like Maut and Prophet where you can go to either one after defeating the fake Wrathion. Meanwhile you kinda have to clear the trash to Inquisitor to get to the Hivemind trash anyway.
Honestly I would like to see less trash in the early stages of Ny’alotha. But I don’t want a raid like ToC where you have to wait for some NPC to shut up after you defeat a boss so you can start even more dialogue before the boss encounter starts.
The reason why Dragon Soul has that annoying dialogue and trash before Ultraxion is because there is no trash to get to Blackhorn, Spine and Madness. It is just boss, boss boss.