I just ran it once on mythic reg to get a feel. Was a mess logistically, but I am sure it will flow better the next few times.
I like dungeons short and sweet this expansion due to the tempo of things. I am sure Blizz looked at Maw of Souls numbers and made the decision to keep it short based on the data.
It was a bit anticlimactic and at the end a couple people asked if that was it. I dunno, I am sure I will chain run as many mythic+ as I can to get the gear I want and hit it up when the weekly is run 4 dungeons for loot chest.