The stated speed of 230mph was probably only reached during a dive. Its cruise speed was 185mph. Incidentally the Dauntless has a range of over 1000 miles - not 200.
Actually most WW2 era aircraft could reach transonic speeds in a power dive. They went to great effort to prevent this since compressibility would lock the controls and the craft would be doomed. Airbrakes were extended during a dive to slow the plane down and allow fine tuning of the aim.
The specs for the SBD 5, the most common wartime version state a top speed of 255 MPH.
The economy cruise of such aircraft was often very low, conserving gasoline was important to maintaining range.
At full throttle the 1300 HP motor of the SBD 5 drank fuel at an alarming rate.
These aircraft were not built for speed, they were built to deliver ordnance at as long a range as possible.