I agree with the guys saying to level the reticle with the plumb line and then see if it tracks... if it tracks, then it's useable, and then you'd just have to decide if having the scope body canted bothers you enough to bother sending it in?
That said, I had 1 MK4HD that the clicks on the turret were spongy and the clicks didn't really ever match up precisely enough with the turret cap to not drive me crazy (but otherwise tracked and worked 100%), then I bought another/different one, and that unit not only had shitty click to turret cap alignment, but also tracked fucked up, and I sent that one back to Leupold and it was replaced under warranty after me hounding them for a month.
I sold the replacement scope without ever taking it out of the plastic, and then was annoyed when the new owner told me the reticle was canted in the scope body fresh out of the box (like the OP describes) when I asked if everything was cool with the new unit and our transaction (he said he was going to shoot/test it and then decide if he needed/wanted to send it in and IDK what he decided).
So take that how you want, but it doesn't seem like Leupold has it together quite yet on putting the MK4HDs together yet, which is a shame since I really liked the glass in mine (and not just for the money) and loved the PR3 reticle... and after getting used to that had to go deeper into my wallet for a ZCO with their MPCT1X to get the same thing I was looking for.
FWIW, I've moved away from a plumb line to one of these so I can sort of test the tracking of the elevation
and windage after an install and before leaving the house and it's worked out good so far when mounting about 4 different scopes now:
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