So today I tried to get Muckbane with my Drow. It took way too many times, but I finally got it!
1st, did it three times on normal, all the way through. No Muck.
Then I tried it on Hard. No Muck, died running around doing optionals.
Then I did it on Solo. All the way through, No Muck.
Back to Hard. Got Muck, but no Muckbane. Recalled out. Then again, and again. So, on my third Muck, got a Muckbane.
On the plus side, I did get lots of xp for the 3x normals, 1x solo, and several optionals throughout. And the festival coins, too!