The last mile problem is only a problem because of poor layout. Build homes and work near transit nodes (instead of in the middle of nowhere) and there isn't a problem in the first place.

> Problems like traffic waves and gridlock go away when all cars are driving themselves.

How would that make those problems go away? It could probably slightly alleviate them in marginal cases, but any given road has a finite throughput limitation, and once it is reached, it wouldn't matter even if every robo-driver were perfectly synchronized.