The Mule has a decent amount of treble, but not annoying or shrill highs. It has tremendous stringseparatuion and clarity, as most BKP's, which you might to get used to coming from Duncans etc. You also might to dial your amp differently.
As a good PAF the Mule is lush with a lot of depth. It can handle gain with authority, without loosing definition.
Use 550k pots and quality capacitors. And use the tonepot to tailor the topend, if necessary. Btw, I have potted Mules which have plenty of mojo.