So i was rendering models from games in Cycles and in some cases the shading looks terrible, shadows are very blocky and there are visible normal map seams. I increased the size of the lamp and tried different lamp types but it had no effect. Adding geometry isn't an option because a subsurf-modifier would cause undesirable deformations in some places. The model came with normal, specular, bump and glow maps which are currently plugged in the Principled shader; shading is set to smooth. Can this problem be fixed or is Cycles not suitable for assets like this?
That looks like a UV mapping issue, perhaps with lighting baked into the texture. Try temporarily removing the textures and see if it looks any better.