Do datasheet specs for a dual diode refer to both diodes in series or to the individual diodes themself?
The reverse breakdown is for each diode. Two in series will yield double the breakdown voltage.

The LTC datasheet specifies the Vishay GSD2004S SOT-23 type with the diodes in series. That diode has a breakdown of 240V (480V combined), so the Diodes Inc device should be even better, yielding a combined breakdown of 600V.