Corvettes are also know as "blockade runners" for a reason. They're fast and are desiged to race past heavy capital ships that are blocading a planet. Thus the game does accurately represent their abillity to race past star destroyers that are sitting in formation.
However, I do think that the game has their health and shields too strong and the devs need to weaken their hitpoints and shields just a little to balance it a bit more. The idea should be that they are light and fast because they can't take too many direct hits from large capital ships. That, and/or make the tractor beams stronger. The corevettes seem to be able to keep going even though they're being tractored. Large star destroyers should be able to tractor corvettes if the player is fast enough to target them before they get out of tractor range.