Don't worry about perfect alignment of the cells.  They are tapered in different directions at the corners, but that doesn't make much difference.  While there are specific corner blocks available, the difference is mostly architectural, not structural.  Show the corner coursing as a running bond, meaning that each side of the corner will show a "half block" (actually the end of the intersecting corner) at every other course.  Horizontal reinforcement should be continuous around corners and typically each corner cell is filled, giving you a three-cell corner filling.

Pay more attention to properly specifying the mortar, cell fill, cell cleaning, and rebar placement.  These are the things that routinely get screwed up...not the coursing.