I think everyone should shoot groups AND a single arrow from different distances and positions.Both kinds of practice has it's merits.
What I hate to see,and I'm not calling any names,is some guy shooting singles that misses by a mile most of the time but only seems to remember the few he lucked in.And the ones that miss half the 3-D targets in a match but claim if it had been a live animal they would have nailed it.
Everyone misses sometimes.What matters is what happens most of the time.