This is something I've noticed a few times. On a print, -A- datum will be called out as 3-4 areas of different heights. (Say, areas 1 & 2 are 133mm in the Z, area 3 is 136mm in the Z, and area 4 is 128mm in the Z) How exactly does this create a level plane? How should I go about my alignment?
Iterative, or best fit, alignments are the best for these type of datum structures. If you absolutely need a plane for datum definition, you can construct an offset plane, or an alignment plane.