There are a few assumptions made in your assessing the problem. The skipping could be from mismatched cassette (wear or indexing not spot on) and der/shifter as example. Campy and Shimano will never say their 11 speed stuff is cross compatible and with the very narrow tolerances the slight cog spacing differences can reduce this even more. The 8 speed wheel you tried... how did you deal with the cog spacing difference? Not shift and set it up in one cog only? Did you repeat this restriction with the 11 speed wheel too?

It could be slipping pawls but we see this a lot less often then what I read here would suggest be the case. Are the current wheels worth keeping around for a few seasons more? If so and if a Shimano cassette compatible freehub body was available I might suggest going that route. Any pawl issue would be moot and you could run a true Shimano spec cassette. Andy