Whats bad about having 4 carriers,more ships the better.
What? No! The more of one ship yes, more of the same ship type doing the same job is pointless. If you're digging a hole with four mates, you don't all grab a different tool just for the hell of it. You all grab a shovel; shovels work. It's the same principle. Having multiple ship types doing exactly the same job is entirely is almost the definition of redundancy. It screws with the A.I., it wastes your resources and it offers no benefit in a game that doesn't have a huge variation in tactics.