First the campaign game is rigged towards having a small fleet due to a
Upkeep is to expensive, in the last epic Imperial campaign i did I never bought any new ships until a C and BCs at turn 11 or so, that gave me ability to buy both at once but my income dropped from 80 to 20-30 something. had I bought a cruiser earlier, then I would have lost alot of income and would not have been able to expand my planets or buy 500 worth of ships in round 10.
Renown bonus is really massive when going against higher value enemies. The most i got was 1500 renown in one battle. Fleet strength was about 400 vs 1000.
This need to be tuned.
Secondly, the AI runs and cap points like a blob at times and the enemy ships stand still while capping, making it really easy to take them out.
Fix the ai so it never caps with more than one ship, preferably a ES.