Oh, turns out you cannot use Spec workflow in UE4 (even if you put spec to 1, that spec has builtin fresnel) Oh well, now that I use the keywords in your post "edge artifacts PBR" I can see that many threads discuss this issue already :)
Wow thanks for the quick answer, that's exactly the problem I'm having, so nice to see that it's not just me (UDN support says I'm the only one having this problem and that I need to learn the basics). quite shocking however that the article concludes that it's an unavoidable problem with PBR, I'm shccked how the whole…