When smelting I find that iron, rusty, bronze, gold, shadow, and agapite have occasional fails but usually nothing that happens frequently. As for the other ores this is the level of difficulty i found from easiest to hardest to smelt: verite, mytheril, valorite, rose, blackrock.
rose has about a 1/3 chance of being succesfully smelted
i havent succesfully smelted a blackrock ore and ive gone through maybe 5 i think since 4.0
I havent mined a single bloodrock ore since the patch. Dunno, maybe its just me?
Anyway this is how things turn out in my case