You'll never get stellar coverage from AI escorts if you're flying the bombers. The best you can do is box your formations so that there are plenty of defensive AI guns besides and behind you as player lead. Unlike you as player, they can draw fire and return it while simultaneously maintaining formation and dropping on target. If you have a mission involving only six bombers with you as lead, you split the flight with you having two radio-controllable wingmen in fingertip or line abreast and then place the other three in an AI flight in the same formation configuration close behind your flight to cover your rear all along the same flight path. Don't leave enough gap between the split flights for a bogey to ignore the "rear guard" and slip in behind you personally. Since enemy AI fighters only engage bombers from the rear, they will have to endure the defensive fire of your rear guard to get to you as the player/leader.
Upgrade all escorts to Ace skill with High aggressiveness so they handle their business faster and rejoin quicker if possible and place them as close as possible to your bomber flights only slightly above and behind along the flight path before spawning the threats. Ace enemies are very sensitive to threats above and behind them, so they will be reluctant to close on your formations without first engaging your well placed escorts. So, for example, instead of a flight of six Oscars coming directly at your flight from the rear, four or five will nervously break and scatter into your escorts as a self defense reflex while any remaining threats stay on you and get busted up by the other bombers behind you.