If you train to use a WML you can do it effectively. If you train to hold a light in one hand and a pistol in other you can do it effectively. If you don't train you'll be lousy at both. There is a reason that "Roland Special"-style pistols are being seen more and more in duty roles. Lights and dots enhance the capabilities of the user. This isn't to say you can't be proficient without them, but you can definitely be proficient with them.