You need SOME way of dealing with AV 14. If he brings a LR crusader or redeemer, you are completely done for.
You could make one of your vet squads have 3 meltas instead of plasmas, that way you can still take marines and then you have some just in case fire for high AV. With the leftover points, you can add a heavy bolter to that last infantry squad, and either add a melta bomb somewhere or make the plasma vets' autocannon a missile launcher.
Quick thing, why do you have a vox on your infantry squad when your command squads don't have one?