Thanks for a detailed answer

I have to say, damn! That is some crazy single target dps you are pushing on the bosses. I'm fully dealing with all mechanics, many times over, for all bosses. And if it is as you say that DK have much higher AoE damage, that must make trash go down very easy as well.
You are pulling trash about the same way as I do, so I guess that it's just the sheer dps output which will speed me up in that (and probably most) mythic+ dungeons.
As mythic+ is all about the speed, and where AoE might matter more in the end than single target, DK:s should definitely have an edge.

You said you started using potions. I had a potion of old war in my bag, and tried it on a dummy. I logged that it did 2 mill damage in total. With Avenging wrath it should do 2.7, and with drums it should do like 3.3 and x5 its 17ish mill.Even with or without drums, that will lower the boss fight duration significantly.

However I'm not even fully enchanted and gemmed yet, and don't always use flasks. So before I start chugging the old war pots I should get those things sorted