The travel times you found are exactly what we experienced in February. As BoB P stated, those are the times from bus stop to bus stop. Genrally we were very lucky and only a couple of times had to wait for more than 5 minutes for a bus, but you really can't count on it.
For DTD the trip was actually a bit longer, I think a bit over 20 minutes, the bus seemed to go a very long way... On the way back we had to wait for about 15 minutes until we got a bus. The general opinion seems to be that DTD bus service is a bit problematic at times. Therefore this would be the only location where in my opinion driving might make sense - unless you want to go there to party (and have a drink).
We generally planned on 40-50 min from hotel room to park entrance for rope drop in the mornings and generally were at the park entrance well before that. But I rather wanted to be the second group through the turnstile (did that at Epcot) than making all the effort just to arrive to lines that already are getting longer.