The thing is, Mentzer didn't build his own body doing one set of pulldowns every 2 weeks.
There were 100's of testimonials on his old site.. and not a SINGLE PICTURE of any of these clients.
the relationships of Intensity/load/volume/frequency have been discussed many many times here, read some of the madcow posts linked in the stickeys to get an idea of why it's a balancing act.