I have to agree with your estimate. I was thinking similar things on a long drive yesterday. Yes, the Empire has hordes of Tie fighters. UN Spacy has hordes of guided missiles.
Contact with the Ties would be made before the fighters actually engage. During the "missile round", the Valkyries would be well out of range of the Tie lasers, and the missiles would chew the Tie fighters up. All this destruction multiplies if the Valkyries are firing MIRVs like the ones in Macross Plus. A cloud of guided submunitions would make short work of Tie squadrons, regardless of their numbers. Then the Valkyries would begin the actual dogfighting on the scattered survivors.
It would be a turkey-shoot for the Valkyries.
Super Dimensions Fortress Macross and all its spinoffs