I recently respecced my SK and took 20 lvls in Resist Cold almost only for the bonus of slowing down enemies. I visually see that the mobs are chilled, but that doesn't seem to slow down their attack/cast speed AT ALL

Haven't really tested it, it's more of a feeling, but having played with this perk on for a bit, I'm left wondering if the "chilling" should be easy noticeable or not...

I can double check if it's applying the chill. It should be similar to a snare effect, minus the slowed casting.

We're talking about the talent where they are chilled when they hit you, right?

Yeah, you're right. I'll patch this in tonight's update.

Sorry, couldn't log in before. The Resist Cold lvl20 bonus says smtg like "all physical damages slows enemies"; it triggers both when I hit them with a phys attack, and when they hit me and take phys damage.
Thanks for the quick fix! That'll help my journey through Nightmare and Hell

PS: so if I read your posts right, it'll slow their attack speed but not cast speed, correct?

Yep! Snare is the only effect in the game that slows cast time.