There was discussion a long time ago about Cryo Blast not actually causing armor debuff. It was all conjecture since I don't think anyone wanted to really spend the time data mining it.
If that's changed, or if I'm in error, I'll certainly take back my argument about not doing anything to armored enemies. That said, I don't believe it's actually working as intended.
And in addition, you're quite right that other powers add the same debuffs while also doing a heck of a lot more on top of that.
But yes... *deep breath* Looking forward to running tests on the cryo blast.
I ran a few checks to confirm things for you folks. Cryo Blast is correctly applying both its damage bonuses, as well as its armor reduction bonuses. Giving it some level of damage bonus against normal enemies, and a more substantial one in most cases against armored targets. I confirmed for you folks that its providing its damage bonus evolutions against unarmored targets as well as armored targets.
I compared with other powers as well, Cryo Blast can provide you a 25% damage bonus, before adding in armor weakness. Warp provides a 15% damage bonus, before adding in armor weakness. Cryo Blast may not be a point maker, but it certainly provides some strong utility to your team.
Happy hunting!