For the Ki-44 I have the climb at 4 minutes and 15 seconds to 5,000 meters, which averages out to 3,860 feet per minute average (1,176 m/min or 19.6 m/s). That's good healthy climb in anybody's book, even next to a Bf 109K-4.
I have V max at 630 kph at 6,000 meters (391 mph), which also isn't bad for the IJA planes of the war.
It has four 12.7 mm MGm so it wasn't without some offensive armament.
All in all, I think it compared favorably with our equipment of the time.
These are Japanese data from a 1946 Japanese book (General View of Japanese Military Aircraft in the Pacific War), not American tests.