Getting chilled in delve with "100% reduced effect of chill on you."

GGG rarely (as in, almost never lol) comments in this part of the forum, and they're the only ones who could confirm specifics for a lot of these kinds of things. We can see quite a bit of info on poedb for ourselves, but not always everything. My assumption though would be that it is indeed working as intended, but maybe not in an obvious way in the course of normal gameplay.

I would suggest recording a video as clear of your own screen effects as possible. Maybe after next level up, so you can just let mobs do their thing and risking death won't matter. Then you can play it back and try to see exactly which mob or effect is causing that 30% chill.

At the very least, then you'll know which mob type to keep more distance from to avoid the chill if it's something you can avoid.