FWIW my step father was a professional stage actor, trained at RADA in Britain, he and others have said that when you're 'doing' Shakespeare you can tell there are parts done by writers other than the Bard. These were segments likely added by later writers, producers, even actors to make the play flow better, build a character etc.
IMHO I don't really care if it was one person that wrote every word, or if like other great pieces of story telling it started with on person and was built on from there to what we recognize as the modern version of the plays. 500 years from now the plays probably won't look like they do now. Trying to figure it out is great fun though.
PC
N P Childs
'I'm Mister Bad Example, the stranger in the dirt, I like to have a good time and I don't care who gets hurt'.
-Mr. Bad Example, W Zevon