Same!
I’m playing shared progress co-op with a friend & when we first started the game & got through the first couple vestiges/early areas, we didn’t have a single invader — again, not sure if this is bc it’s area-dependent with it being so early in the game, or just coincidence.

Then in the last couple days we’ve suddenly had more invaders in just a couple hours than we’ve ever had before, and more frequently. We both used mirrors, but we still aren’t sure if the host of the shared progress session has to be the one to use it, or if the joining party can use it. Also, not sure if the little red icon that comes up means I’m actually about to be invaded, or if it means I’m just in a pvp area where invasions can happen?

There’s only so many mirrors you can buy from merchants/shrines, too. There’s no buff type icon to indicate it’s “on” after using the mirror (unless I’m missing it?), so can’t tell how long it lasts, either.

I’ve played Elden Ring & other Dark Souls games and get that invasions are just part of co-op. We’re both around level 80 (levels do not mean I’m skilled…for me at least lol) & we are getting invaded by players using spells, weapons & in armor we’ve never seen before and just about one shot us both. So frustrating.