Thank you, that makes sense. Clearly they're just wanting to increase the power of the pickup as much as possible so that it can live with the Super Distortion. DiMarzio said the output would match a Super 2. This sounds ideal, but they also suggested I might be worrying about a non-issue. For a start, they warned that the output might be more than I want in terms of articulation with gain. They also pointed out that as long as I'm playing with gain, having a lower powered neck pickup won't matter because the clipping tends to even out the output.
If all this is true, it seems to me that I might as well just go for the pickup that best offers the tone I'm after and not worry about power (within reason). That does, of course, confuse matters because it throws a whole range of possibilities into the mix. The PAF Master neck may still be too weak, but the normal bridge may work OK, and both of the PAF 36th Anniversary pickups might be suitable. Could the PAF Joe also be a possibility? Presumably there is also the PAF Pro, though DiMarzio described that pickup as being 'edgy', which didn't sound like the Dave Murray tone.