My amp is a Shishido 805, which is the basis of the Wavac 805 (effectively the same). I find it a truly stunning amp - I think there is an early review that pretty much sums it up. What is wrong with it?? You would have to hear it, and then maybe you could figure out something wrong with it - I can't think of anything, The amp is driving a pair of Altec 604 drivers in 9 cu ft cabinets. Tons of power, and the amp has the drivers in a vice grip with regards to control and presentation.
The Wavac secret sauce is likely the Tango transformers, custom wound by extraordinarily skilled craftsmen in Japan for the Shishido design. Hirata Tango for mine, ISO Tango and apparently Wavac for the later variants. You can likely find response curves for the special transformers on the web - my book shows the output transformer flat from 30 to 40K Hz (0db down). Also there is an interstage transformer, so no caps in the signal path. A simple, yet highly competent amp using stunning parts.
Seems like nobody else has actually heard a higher power set amp like the Wavac, and yet they are fine saying they don't sound good, or it cannot be done. Not sure how they feel comfortable doing that. If you have a chance to hear one, then do so. It might well change your perspective.