The reason that Epcot sort of disappoints at this stage of its life is that there are so many of the original designers that aren't there any more to protect their visions. Things have been "re-imagined" in ways that they were never designed for. There are so many beautiful spaces that sit empty...
Don't let the forcasts worry you. That can change in an instant. We've lived here 29 years, and there are very few all-day rains. Usually an hour or two at most then it's over. It cools the weather down and is usually quite pleasant afterwards.