This may not be the issue but it would seem like The nexus servers kinda work on a seeders and leechers system which means that the more people use the same server means the faster download will go, I tried this theory by manually downloading the "Willow Better Companion Experiance" mod, in the Salt Lake, USA (N15) only had about 3 users downloading and my download was very slow, then I tried the Washington DC server with a approx of 113 users and my download actually worked, while my mod manager downloads very slow or won't download at all sometimes. I believe that nexus should either have a wider range of what server you would like to download in or improve the overall performance of the mod manager. test this theory out for your self and I am very sorry for my poorly written english. - Random none technical dude.