Well they're tiers for increased amount and such. Like a tier for increased threat for example. In my full darklight armor, I'm 10 str points away from next tier for threat increased, however I put all 30 points into Vit because I prefer more health over more threat since I don't really have problems with threat management.

And I can get the extra str from higher item level gears anyways. Hope this helps. And it has been proven, there was a guide about it. Don't have the link though.