This article, written by a noted wargame designer and air war historian gives some data on hit percentages for torpedoes and dive bombing against ships.
DT might find it helpful in establishing baselines for dive bombing and torpedo bombing accuracy, since it involves pilots of known skill aiming against targets of a known size from known altitudes.
http://www.ospreypublishing.com/arti...en_it_counted/
Takeaway
Japanese at Pearl Harbor (i.e., excellent torpedoes, Veteran or better crew who had trained extensively for the mission, and who were attacking static, battleship-sized targets) achieved 37% overall accuracy - which was exceptional.
Level bomber accuracy for all other skills and nationalities was 1-3% in 1941, but Japanese pilots preparing for Pearl Harbor were getting hits 14% of the time, from 8,500 feet. At Pearl Harbor, they hit 43% of the time with level bombing attacks.
Up until 1941, German Stukas (all skill levels) achieved 25% accuracy in dive bombing attacks. Japanese dive bombers were hitting practice targets 30% to 34% of the time; at Pearl Harbor, under fire, their accuracy rate was at least 26%. So, 25% dive bombing accuracy while under fire is probably appropriate for Veteran pilots.
By late 1944 the US Navy was pleased to achieve a 40% accuracy rate for practice torpedo bombing (i.e., presumably Rookie level pilots). In training the Japanese torpedoes were hitting 70% to 80% of daylight targets and 50% to 75% at night; at Pearl Harbor their accuracy rate was 51%.
According to the US Navy 20 torpedoes hit American ships. Only the 40 Mitsubishi 'Kate' torpedo bombers of the first wave carried torpedoes. The USS Nevada shot down one 'Kate' before it could release its load, so only thirty-nine torpedoes were dropped. Twenty found their mark = 51% hits.
So, 50% or so can be taken as the maximum accuracy level for a Veteran or Ace torpedo bomber aiming against a static battleship while under light and inaccurate AA fire. Assuming that combat effectiveness of torpedo attacks is reduced by 30% compared to training runs, perhaps 10% hits for Rookies making daylight attacks, and 1-3% for night attacks would be realistic
In the first wave 21 of the 49 800kg high altitude bombs scored direct hits on the battleships USS Arizona, California, Maryland, Nevada, Pennsylvania, Tennessee and West Virginia; three more damaged the USS Oklahoma with near misses. The Japanese pilots targeting battleships had a 43% accuracy rate, 49% including near misses. In either case, the Nakjima B5N 'Kate's' level bombing was far better than predicted and much better than the 13%-14% achieved before intensive training.
In the second wave, of 80 bombs, 21 were effective, a 26-27% accuracy rate which is still less than the 30%-34% scored in practice. The difference is accounted for by the fact that the pilots were diving into smoke and evading flak.
So, medium-altitude level bombing by light bombers piloted by Veteran aircrew should have about 43-49% accuracy in combat, reduced to 26-27% if the target is obscured by smoke and/or planes have to deal with flak. Average to Rookie level level bombing in 1939-41 should have dismal results with just 1-3% accuracy, especially if dropping bombs from higher levels or in combat conditions.