Modern firearms have an extremely high rate of fire and travel fast as hell. It wouldn't be deflecting a bullet, it would be deflecting dozens or more bullets effectively all at once (never mind if there was more than one shooter).

I forget what their energy weapons travel at, but I recall it being a fraction of the speed of even your basic M4 (never mind something like a sniper rifle or anti materiel rifle).

Even a shotgun slugs would be a big problem once they hit the lightsaber: They'd probably explode and pepper them with semi-melted lead spall traveling around 1,500-3,000 feet per second.

Seems like it would actually be more of a liability than just taking cover, retreating, or maybe using the force to either escape or deflect them.