Gotcha, that is by design. The Dunov is considered a support ship so we set the combat distance to be determined by its bigger weapons. This keeps it as far away from the target as possible while still doing a reasonable amount of dmg (low armor pen, low dmg PD shouldn't contribute much). PD in this case is really just to keep it alive if there is a missile or strikecraft attack to the rear. We may need to rebalance its PD if is doing a lot of dmg but we haven't focused much on balance yet.
As you discovered you can override the default behavior by moving the ship closer.