Went back to see if there was a bug with focused secondary fire. The one ship in the three above that was killed in under one minute was the one I didn't focus guns on. Additional testing showed nothing... kill rates are all OVER the place for the Myogi.
Something else to keep in mind is just how bad even the main guns are on the Myogi. I had a few minutes left in the training room and not enough time to move to the next DD and time how long it took to kill. Instead I simply fired HE at it. I got off 32 main gun rounds and hit... all of 4 from a distance of under 5km! I took off all of 6k dmg from a 9k hp pool ship and half of that was from a fire I set on my first hit.
BBs are fine... once you get to high tiers. Low tier ones are borderline unplayable. RNG is just too prominent.