Maybe it would help? The fighters alone seemed to do just fine at assaulting the Death Star and CR-90's are still very susceptible to turbolaser fire, of which the Death Star has lots of. CR-90's are smaller and more maneuverable than Nebulon-B's and larger but they're not going to be able to avoid turbolasers the way X-Wings and Y-Wings can.
And again, sending in a larger force than what was shown in the movie also assumes that Empire would respond with a larger defense force. So not only will there be many more TIE Fighters, but it may be safe to assume TIE bombers are sent to clean up the CR-90's that aren't being picked off by the Death Star's turbolasers. So now the Rebels have to split their forces between trench run and defending their corvettes.