Well, i looked into them and the way air raid works is that is a final 15% additional damage delt on top of the sum of damage dealt from skills and gear and stats.
So if enty deals 200 damage as final damage (of course she wont deal this low) that 200 damage is then increased by 15% via air raid. Kearsarges skill works exactly the same. Which us why it doesnt stack.
I'm not all that knowledge on fleet building, but I have spent some time to look into damage calculations. So even if kearsarge herself is only applying burns and skill based damage (which i have her skills maxed) even if she underpreforms in that regard, shes skill giving enty a giant boost in damage.
I also don't really any ships with air raid that aren't blues (which i usually dont even have) anyway. I could swap her out with another CV but i have no other cv who has leveled skills because I never really uses them.
Im not trying to argue and say that kearsarge's skill provide more than enough value, but im just saying they're the only value i have.
Also I may swap fdg out with war spite, i just neglected to do so because originally i put fdg in the mob fleet to act as extra securiry just in case of suicide boats. I normally dont use fdg much because I don't have the proper gear to spare for her and because, as mentioned before in previous conversations, her dev level isnt at 30 yet and i havent begun fs so shes a bit underpowered