Two shots won't prove a load to be consistently accurate, but two shots can definitely weed out the chaff.
I've used two-shot groups when starting out with new component combinations, looking for pressure/velocity. Might as well get the easy data while you're starting from scratch. Two shots in an inch and a half says "don't waste your time here.
My thoughts, too. Use 2-shot groups to find max pressure, and also to see what doesn't work, at the same time, i.e. a third shot never shrinks a group. Then, shoot 5-shot (or 3-shot) groups around the area(s) that first showed potential with the 2-shot groups. Same general process for finding seating depth, too.
Like this:
Resulting in this: