One of my guards has DR 14 and HA 13, but IS 2 (popped to 3 only last week). He manages to hit 50-60% of his layups. I think HA is also important when considering the effect of DR.
That being said, two seasons ago I had a player with DR 13 and IS 7. He always played at SF. It seemed like he scored more layups than my previous guard.
However, when the above mentioned guard drove and found himself in front of a C or PF, he almost never scored.