I never use Edern/Effie/berched for my repairs, their repair rates are a lie.
Edern seems good, but I can understand Effie, she fails a lot on my stuff... I haven't gotten any failures with Art on instruments, though.
Also I don't know if it's just me, but it seems like the blacksmith in Cobh and Tara Stonehenge rarely/never fail... Nicca seems pretty decent too.
Nerys is the one to watch out for... I have experienced so many failures in the few times I've used her. D:
PS: I do hate the durability system as well, but I know a lot of people also would want to keep it because of the gold sink factor... Well, it would be nice if they at least let broken items be equippable and maybe just disable/penalize their stats?