Every D3 is different, so there are no general settings that fit everybody. Even in a single D3, the boards can be very different, and this is the reason Blissz added the individual board tuning feature.

You should just follow these instructions (courtesy of Blissz):
Start with frequency of 400 and a "Low" voltage setting.
Then increase the frequency until you start seeing HW errors.
Now either reduce the frequency if you want to keep the lowest power consumption, or increase the voltage incrementally until the HW errors disappear altogether, or are not more than 12 per hour.
You should also keep an eye on chip temperatures of each board (or chain), and try to keep them under 80 deg. C. using the fan automatic profiles or fixing the fan speed at a certain percentage. I prefer personally to keep it on automatic.

As a rule of thumb (at least in my 19 GHs D3 batch from mid October), the highest frequency I can use without HW errors on "Low" voltage is 438, some boards cannot tolerate higher frequencies, and they start producing too many errors already at a frequency of 425 or even 419!
 

Tuning each card I discovered that changing the voltage on one of them also affects the number of HW errors I get on the other ones. I don't know if frequency has the same effect. This made it quite tricky to get the three cards tuned independently. Have others observed this? What would this happen?

Wow after last update my OC settings do way better  with less hw and temp !! stable 22gh with 73 temp no hw  !!