I found the same thing when I was playing through my cab with Celestion G12S-50's. The only hi gain profile I liked was the one I made myself with my JCM800 2210 and a modded SD-1. I was borderline going to sell the Kemper until I profiled my own amp.
Now I'm running Kones I'm really liking a lot of other profiles, a particular 50w plexi profile with the gain pushed up slightly is now my go to rig. However I can't get the profile of my amp to sound any good through the kones at all. I'm only now starting to realise how dark my old speakers are and how well they're matched to the overly trebley sound of the 2210, they really throw a blanket over most other Kemper profiles though.
It makes sense that your sound through your gear is going to sound best. However awesome the Kemper is it pays to remember, particularly for hi gain sounds that the speakers and cab your playing through affect your sound possibly more than the amp itself.
One other thing I've noticed is that a lot of the hi gain rigs have been profiled with scooped mids and poor string definition/clarity (I guess that's what most other hi gain players like) hence why I tend to go for slightly lower gain rigs that sound better and then tweak the gain to taste