I did quick testing of shadowcatcher's compositing mode fix. It looks that finally it works! :]
2 minutes limited run:
1.7.2
solid mode: passes - 23, noise - 3,99
for compositing: passes - 29, noise - 8,87
DB 01-02
solid mode: passes - 19, noise - 1,72
for compositing: passes - 19, noise - 2,20