Hi Artaekos I honestly do not see a problem with that obj you sent (apart from an overlapping uvs complaint from UDK) I exported your file from modo to FBX 2006.11 and converted it to FBX2013. The light map res is 256 and this is my result: I would be happy with this and as Quack! said once the diffuse is on there it looks…
Baked lightmap shadows don't look good on their own. Once you have a diffuse on there, the lightmaps lack of resolution isn't so apparent. With that said, your lightmap UV's islands need to have a TON of padding in between them, or else you get shadowbleed and nastiness.