Is it possible to set change for spawning rare thralls?

I know it can be done with modding. But is there some server settings? I would like to have t4 thralls spawn rate over 40% at least. It is booring to grind t4 thralls for weeks((

On an official server, NO.

We can make level 20 in hours, 60 in a day or two, and have all the thralls we want building a place outside of Set City. We have the major thralls in a few days, not weeks.
You may want to review your play style.
Modded it even easier.

Beastmaster Teimos is like a 50% spawn chance and he’s pretty much the META PvP thrall anyways

You can’t change settings of the official servers)) I know that. I asking about private servers/singleplay

If you play a lot and not alone - yes.
But couple of hours per week - max with one-two friends - this can take some months

Dont care about pvp - much more for recipes

Sinner’s Refuge has T4 crafters that spawn often. For a T4 armorer that spawns reasonably often, go to the 4 Relic Hunter Slavetaker camps and you should be able to get a T4 in a reasonable amount of time. He only crafts flawless DLC armors, but it’s better than having nothing.

As for the rest of cultural armorers and blacksmiths, I really, really hate the slot machine mechanics involved in getting them and I wish Funcom would either increase the spawn rates or get rid of the concept altogether.