The best blacksmith is Edern in Bangor. He has a 98% repair chance, which is even higher if you bless your equipment before you let him repair it. He is, of course, also the most expensive one. Also, make sure you don't mix him up with Elen who's right next to him and has a much lower repair rate, and if you decide that blessing your items is the way to go (which you should), make sure you repair only one point at the time so you can re-bless your items if your repair would fail (which removes the blessing). A "complete" repair is a bit tricky in that it still does each repair individually, so if you are repairing 10 points for example and "failed" the first repair, it'll do the next 9 repairs without blessing.
Best of luck!