From playing extensively with the slowest blockable weapon in the game, the pike, I can tell you with little doubt that weapon speed does influence your blocking speed. Blocking with a pike feels sluggish and awkward, like you have to work for your blocks. Blocking with a 100 speed weapon seems instant and feels much better. It's sort of less 'snappy' with a pike if I had to describe it. I often block and backpedal my way out of sticky situations with a pike and I actually miss blocks sometimes, while I can't say I miss much blocks when focusing on defending with other weapons. Not sure about the exact mechanics behind it, but quite sure there is something.
As for wpf, I am not sure, but I'd say it does not influence your blocking speed. I have duelled with one handed weapons without wpf enough and I always felt like blocking was as easy as it normally is.