DME is not intended to be a 'luggage delivery service'. It is intended to get WDW resort guests to their resorts as efficiently as possible, with a side perk of not having to haul your luggage around the airport. It, at least some of us believe this to be true, was intended to keep the resort guests on-site, spending their cash within the confines of WDW...rather than traipsing off, over to Universal and eating/shopping there or at any other of Orlando's fine eateries.
So, if you want to rent a car, that's fine. But you can't count on DME delivering your bags if there is no one riding the bus. For those of you who wish to split up your parties, and have some ride the bus, while others go in a rental car, that will work just fine. Many do it this way.