This posts summarizes my own experience very well (IJN CV player here - currently in Taiho).
Bottom line with 0.4.1 :
Yes CVs needed to be tuned down, especially IJN strike setups The tune down clearly appears to be overnerfing, not necessarily vs other ship classes (no uncontested sealclubbing anymore - for the better), but more specifically vs USN CVs (as stated above) As most other players have indicated, Fighter Barrage is useless at the moment.
I believe that a slight change to torp spread (a bit tighter, but not as tight as USN TBs) and slight overall IJN planes survivability increase would put the balance right where USN and IJN CVs are more or less on par, and neither no longer roflstomp the rest of the game