Having an easily exploitable weakness isn't necessarily a bad thing. It just means that Shadowdancer has to work around it. Like how Batman has no superpowers and often is deprived of his utility belt, but he's also a martial artist and can think quickly under pressure, allowing him to do his job fairly effectively even without his "superpower" (i.e., his utility belt). Normal UV flashlights are only as effective as the aim of the person holding it, and if it merely burns SD and removes her powers, that's not gonna stop her from rushing the bad guy and punching his lights out (pun intended). As for UV floodlights, that's something SD would have to scout out and plan ahead for before she acts.

I dunno, that's just my two cents.