I couldn’t damage NMD Uldur’s cave’s barrigades with rogue’s rapid fire with or without cold imbuement. I tried to aim it differently a few times but it made no difference.
I had the following uniques equipped:
Skyhunter
Cowl of the nameless
Scoundrel’s kiss
Condemnation
and following aspects:
concussive strikes
expectant
umbrous
frostbitten
repeating
coldclip.
On paragon board I had the following glyphs activated:
combat, control, canny, fluidity, ambush
and legendary nodes:
exploit weakness
tricks of the trade
cheap shot
deadly ambush