In true BKP forum style, here's an alternate suggestion (no "which pickup" thread can be considered complete until at least ½ the entire BKP range has been suggested :lol:)
My reading of your post is that you don't mind the power of the DiMarzios & are quite happy to back the volume off, but it's the lack of clarity that really bothers you. In which case, a Cold Sweat calibrated set ought to do the trick nicely. CS has absolutely bucket loads of clarity, power & hot rock tone, but unlike so many ceramic bridge pickups, the bridge has a sweet clean sound too. CS is absolutely perfect for heavy Les Pauls.
FWIW, I have very little experience (OK none :)) of middle position humbuckers, but I'm guessing that a middle postion CS in a 3-pickup calibrated set would be a neck model, perhaps a little underwound.