Sabers he matches or even better him, especially if using dual bladed techniques, but it's made pretty clear--one of the few things we actually get enough details about--that Kas'im and Lsu's abilities are much greater with sabers than with the Force. So in an all out fight to the death from the start where Galen isn't hesitating to utilize everything at his disposal Kas'im falls. If we're assuming the same setting then overall Kas'im doesn't have enclosed space to keep it to his advantage with sabers only.