Corona's EV is arbitrary, you can't compare its default valueas to real world camera. What you can do, is to take picture with the camera outdoor at noon, write down shutter speed, ISO and aperture, then create scene with default sun & sky in Corona, switch exposure from arbitrary EV to photographic, enter values from your real camera and compare render with the picture. Exposure wise they should stay pretty close to each other.
Making sun & sky at 0.1 by default, would be really bad idea. What you might want to do instead, is to request to change default EV value to match daylight scenario, although current setting has its own reasons and i wouldn't like it to change just because someone does more exterior renders than interior ones.
P.S. i'm moving this topic to main feature request board, as we certainly don't want that common defaults would differ between different DCCs.
