How about shifting that ability like so:
Shadowy Form: Shades are partially composed of pure shadow, and are at their strongest in complete darkness. Shades get a +10 bonus to Hide checks against creatures with Darkvision in complete darkness(Creatures without Darkvision or another supernatural sense cannot see at all in complete darkness), a +4 bonus to Hide checks when it is not daylight, and while at least partially in shadow, their form is somewhat mutable, granting them a +2 Dodge bonus to AC and a +10 to escape artist checks. They take 2d6 damage from initial exposure to any magical light source (Any given spell only damages them once) and are unusually vulnerable to light, taking damage from spells as such(For example, Searing Light impacts them the way it does a Vampire).
Light Blindness: A well-illuminated target or a completely lit area, such as an open field during daylight, has total concealment from the Shade, and Shades will avoid such at all cost. Simply bearing a torch is not sufficient to be well illuminated, but wearing a brightly glowing suit of armor or something similar would be.
