There's not too many busses ever go direct from resort to park. Some make multiple stops at one resort and a water park and others stop at multiple resorts and a water park.
WL is the first stop for the bus that goes to the Poly, the GF, and then to one of the water parks (?Typhoon Lagoon) before going to either AK, Epcot or MGM. Coming home, it seemed to stop at the water park again, and then WL, Poly, and GF. When the bus is full, it will proceed directly to the parks.
Of at least 30 days that we've spent at WL, we've never experienced terrible bus service. However, in 25 trips to Disney we have had a very few frustrating transportation situations (45 minutes for a bus at CS and DL, 35 minutes for a boat at WL). It seems to me that there can be a difficult situation on any given day at any given resort. I've never experienced consistently slow service over a period of many days at ANY resort. There certainly are times when we've waited 20 minutes for a bus and I wish it wasn't that long, but that's what Disney tells us to expect. I'm sure that we've waited less than that at LEAST 75% of the time.