Is it acceptable to use a cut edge against a tapered edge at a drywall joint?
Almost any larger drywall job will have a few odd cases like that. Good tapers run their butt joints 18" wide or more as a rule. Hiding a tape overlay in that width is not difficult. Use a wide knife or trowel, but keep things thin. Remember that sanding is really only intended to knock down tiny imperfections, not shape the wall.