Feb 24th 2009 10:58AM Taken from MMO-Champion:
"Glyph of Mirror Image *new* -- Your Mirror Images gain the Winter's Chill talent, granting their Frostbolt spell a 100% chance to apply the Winter's Chill effect, which increases the chance spells will critically hit the target by 1% for 15 sec. Stacks up to 5 times."
The WC debuff currently gives 2%, stacking to five times, which brings it to a consistent 10% crit chance on a target.
Maybe the WC debuff'll be nerfed to 5%, which would mean scorch is next, or maybe the MIs just get a crappy version of WC.