I know that sound what the OP is talking about, been listening it for the whole time I've had Kemper. I've been trying to solve this issue for so long time and I've always knew that this isn't the way Kemper should sound. I can finally say that I have solved my hardest puzzle in my life and yet the solution was so simple. Electricity.
We live in a house that only has grounded outlets in our kitchen. Today I plugged my Kemper into one of the grounded outlets and holy sh*eet, is this how the unit is supposed to sound?! No more dirty high end and all the profiles actually sound different! For some reason this affected the whole signal chain so badly that I had to drop the input gain in my Kemper for ALL my guitars for about 5 db down. I always knew something was messing with my signal chain but now it is pure as it can be.
I don't know why I didn't try this before but OP as you mentioned in one of your DM's you sent to me that your house doesn't have grounded outlets and I'm pretty sure this is the issue.