Playing with carriers lately, and on watching drovers I think there is something wrong with the way the fighters that spawn from that ship are treated that is impacting their performance.
Sometimes when bomber wings return from a strike, even when all of the fighters survive a fighter will enter 'rebuild' instead of 'rearm', greatly impacting the replacement rate of the ship. Other times, fighters that have been orbiting the drover for a while, and are full on ammunition, with the ship system not active, will dock with the Drover and require complete rebuilds - I've seen the entire wing of a 2 fighter per wing group do this, requiring a full rebuild which tanked the replacement rate. The upshot of this is that even when they are not taking fighter losses, Drovers are constantly doing rebuilds of individual fighters so their rate never recovers.
For me the first of these happens reliably and the second occasionally in a mission screen fight of a AI controlled Drover vs the sim Mule (a decent punching bad that survives but rarely shoots down fighters). Build on the Drover (somewhat random): Dagger, Longbow, Vulcan, Railgun, 2x swarmers, expanded deck crew, 15 caps.
To see it faster under player control, activate the ship system while bombers are returning from a strike and blacked out: the ship will spawn new fighters, the old ones dock and no new ones come out, and then after the new ones have fired their ordinance and returned to the ship they will not rearm, but instead rebuild even though no losses have been taken.
I'm not sure how the 'extra' fighters from RD are being treated, but my wild guess is that what is happening is the the "real" fighters are docking with the carrier and getting deleted as the current fighters spawned from the ship exceeds the wing limits, but then the 'reserve' ones later rearm/dock and don't spawn immediate replacements.
