What bass and cabs are you using? Bear in mind the response of the amp is pretty much flat, so whatever the bass is putting in, is going to be well reflected in the out. Presumably you haven’t got ‘bright’ engaged, and you’re using flat at a starting point..?
One way to take out a bit of the high mids would be to dial in a little bit of the contour.
I was a long-time Mpulse / WA user, and while the EQ is far more flexible, I found myself mostly using it to try and put the mids back in.
Either way, I hope you manage to sort it after a bit more tinkering. I don’t like a toppy sound, but it’s perfect for me just left flat or thereabouts - it’ll be interesting to hear how you get on!