I think the Jepetto quest was a bad, greedy move by Blizzard to try to sell more Tavern Passes. I’ve also said in this thread that I am personally cutting back on my spending on Hearthstone, and if the Jepetto quest had come out before I bought the Tavern Pass, I probably would have avoided buying the Tavern Pass this time around too.
That said, I will repeat that I would not expect any retroactive achievements awarded for killing Jepetto when the quest was bugged because I do not think they have ever implemented any such “fix”