I'm a big believer in there are so many ways to cook bbq and not swearing off any one technique. I still don't get mustard at all though. Seemed like an extra step that didn't add much if anything. My rub sticks to meat great without it. I have been wanting to try mayo on chicken though recently. But some folks love it. Mess around with dropping it and see what you like if you haven't.
Wrapping is your culprit more than likely. I wrap and my bark is soft, but nothing wrong with that. I'd keep everything the same (including mustard) but wrap in butcher paper or no wrap and see what happens. Don't change too many variables at once or else you don't know what affected the end result.
And make sure you like the extra bark and not just doing it because others do or to more impress your friends who might not even care
. Have fun experimenting! Oh and for home I started cooking hot 325-350 so the cook goes faster and still gets great results. Maybe in the future give those hotter temps a whirl
