Unicum carriers end the match immediately by killing all the DDs. I've experienced that firsthand, not anecdotally. And there is no way for a DD to overcome this problem, except for retreating near his friendly carrier. As a BB, however, I can definitely affect a match's outcome, seeing better win rates in certain ships. So I don't think carriers really mitigate unicum players.
IMHO, carriers should spot general minimap location, but not cause ships to be properly spotted (like what happens in storms when friendlies are far apart). If the carrier were close enough to its own airplanes, then sure, share the location. This would encourage carriers to get closer to danger, making them more vulnerable, but rewarding them for taking risks.
Right now carriers are super unbalanced because they continuously spot. Because spotting damage only happens after a certain time of not being spotted, and because much of the damage caused by CV spotting is shared by the team (eg. cruisers shooting down DDs), this excess is probably not noticed by carrier players or by Wargaming spreadsheets. Also, the rate of new airplanes is just abusive.
Aircraft carriers in WWII won the war and made BBs obsolete and changed naval warfare. So of course they are overpowered in a BB game.