The Town Alchemist success rate was initially 60% and the cost was low to favor the mining of veins in the first month of the server - in short, it was as such to allow players to have refinements on their equipment without too much of an investment.
Then, as you noticed, when more and more guilds acquired Lands and an Alchemist, they instantly pushed the patch which reduced the success rate of the Town Alchemist to 20%, and probably keeping the same cost of refinement there. In short, the 60% rate was there for server start only.
So, technically, they did increase the success rate.
Refinements are a nice bonus, indeed, but not needed by the majority. This is why I see it as, more or less, something optional. This is why I also agree with the fact that ingots and Diamonds should have a higher cost - both price on the market and cost to make. After all, let's not forget that you can pretty much AFK mine in temple all day long - there would be either a decreased success chance to refine ores or a higher cost to do so. I'm happy with the higher cost as it favors casual miners as well. The way things are right now also prevents the market from being flooded with ingots and Diamonds.
The bug where the Alchemist doesn't take your Yang will probably be fixed with the next maintenance, so I wouldn't count on that either. AFAIK it only happens when members of the guild that owns said Alchemist try to refine.
EDIT: I can say that, as a map1 farmer, 300k to refine Diamond and 200k any other type of ore is an abysmally low price to pay for 60% chance to refine. I am comfortable with that.
