I’m doing some research right now for a daisho that I will be listing soon. As part of this, I counted the top ten smiths by simple output of blades ranked Tokuju, Juyo Bijutsuhin, Juyo Bunkazai and Kokuho combined.
This is the list as a simple point of interest.
- Osafune Nagamitsu 
- Rai Kunimitsu 
- Osafune Kanemitsu 
- Soshu Masamune 
- Rai Kunitoshi 
- Saeki Norishige 
- Rai Kuniyuki 
- Osafune Kagemitsu 
- Niji Kunitoshi 
- Ko-Bizen Masatsune 
Some notes on this… Niji Kunitoshi and Rai Kunitoshi are the same smith by modern standards. So if we add their output together he places second overall, with 96 total works, and this would move Masatsune into 9th slot and Soshu Sadamune will then slide into 10th spot.
Both Nagamitsu and Rai Kunitoshi benefitted from having large numbers of high level master smiths working under them. Kanemitsu and Kagemitsu also both benefitted from this.
But the interesting thing for me in looking at this list is how it is almost evenly split among Kamakura period Soshu, Rai and Osafune output. It illustrates very well the reverence in which these schools and smiths are held.