simshell,
Against condensed, soft targets the Ki-67's payload, if you take the eight 100kg bombs, does nearly as much damage as a Lancaster with 14,000lbs of bombs. The Lancaster achieves massive overkill.
At 20,000 to 22,000ft and at full throttle set the delay on the Ki-67 to .40 or .45, If you are hitting a target that has one long path of targets, set the salvo to eight. Against the city that I bombed the other night I set the salvo to four and hit two different sections. In total I got about 15 to 20 buildings.
The other advantage the Ki-67 has is that it is fast and climbs very well for a bomber. These both cut down on trip time by a lot.
With two 1,900hp engines the Ki-67 could have lifted a heck of a lot more, but the Army specifications were for an 800kg bombload and that is what Mitsubishi delivered.
I think the Japanese were a bit unclear on the usefulness of a heavy payload. Only the G4M with a 1,000kg bombload and H8K2 with a 3,000kg bombload carried more than the Ki-67. It seems that the Japanese standardized on the 800kg bombload, regardless of the type of bomber.