An editor I work with says that he has a shelf full of dictionaries, and he can justify pretty much any usage he wants if he looks long enough.

But back to MW11 . . .
I looked up "discursive" in Merriam-Webster's because it's a word that I always think of when I'm actually trying to come up with something else -- a word that still eludes me -- so I want to make sure I'm using correctly whatever word I'm remembering or forgetting.
Here's Merriam-Webster's 11th on "discursive":
1a : moving from topic to topic without order : RAMBLING
1b : proceeding coherently from topic to topic
Ehh, maybe it's time to switch allegiances.