I've always been ticked about this too. From everything I've heard Jason was basically told to stuff it anytime he mentioned anything related to bass because he wasn't Cliff. So he basically doubled James and let the band do what they wanted with the tracks.
The mix itself is so guitar centric because it was partially produced by Mike Clink (the same guy who gave Appetite for Destruction its signature, ummm, sound). Mid way through the project Metallica brought Flemming Rassmusen back to try and rescue it....but the damage was done (especially the bass tracks).
Also if you think the overdub work on Justice is too much, the black album has TWENTY FOUR tracks for each rythym guitar part

The mix itself is so guitar centric because it was partially produced by Mike Clink (the same guy who gave Appetite for Destruction its signature, ummm, sound). Mid way through the project Metallica brought Flemming Rassmusen back to try and rescue it....but the damage was done (especially the bass tracks).
Also if you think the overdub work on Justice is too much, the black album has TWENTY FOUR tracks for each rythym guitar part