The gain/output is something that bugs me too with my Holy Divers and BKP's in general. Maybe it's the definitions we use of gain, saturation, and output, the Holy Divers are very "saturated" gain-wise, but the output power seems low. I use to use Dimarzio Super Distortions and JBs, and I switched to the Holy Diver to get the characteristics of both in the same pickup, and while it does do that, it's missing the power and punch, and I find I have to use a boost pedal to the HD where I want it, but it's still not the same.
The Holy Diver has it's own qualities of course that are improvements: clarity, holds up under high gain, smooth saturation, fluid leads etc... but they are also very polite sounding for lack of a better term. I keep missing my Dimarzio's for the sheer power.