Faction played: Rohan
Map played: Tarnost (latest), although I've noticed this issue occurring in multiple maps
After playing against the Captain AI Isengard in one match on Tarnost, I noticed that the Freezing Rain CD seems to have a 25% faster cooldown than what it should be as a mapwide 15 PP power. I cast Ere The Sun Rises (Rohan's mapwide 15 PP power) shortly after the Isengard AI cast Freezing Rain as a counter measure, yet despite casting Ere The Sun Rises immediately after Freezing Rain, the AI was able to cast Freezing Rain again when I still had 25% of the Ere The Sun Rises CD remaining. Both the enemy AI and I had each captured one signal fire, so I know for a fact that signal fires didn't impact this.
Other mapwide powers cast by Captain AI (Darkness, White Winter) did not have this issue, so I'm fairly certain the abnormally fast CD is specific to Freezing Rain.