Aww, man.

You guys completely wrecked my game strategy. Maybe it was an exploit that you corrected; I never really thought about it. With Speedy Crafters/Speedy Smelters, I had them upgraded to rare (25% faster) and was going to upgrade further because toward the end of the game, you have those valuable items that take like 4 hours to craft. I could just pop on, change the artifact, and boom, get them an hour early. It's going to take two hours to smelt those? Nah, pop on in an hour and a half and get them early. Get them, sell them, buy the mercenaries (which I've upgraded with AP), and finish the level fast. So it's not just strategy with artifacts, but it's my strategy with AP placement that has been wrecked.

It really sped up the game. I was looking forward to getting them 50% quicker after upgrading. Now it's gone unless I keep the artifact in hold (I'm assuming: Haven't tested it).

Yeah it sucks that it was changed, used to be one of the best artifacts, but honestly I always knew it was broken and now it's working how it should been from the beginning. The game is still in Beta, so you should expect things to be tweaked. Epic was only 35%, not 50%. I have a rare of it and at least now I have an easier choice on what to sacrifice when I upgrade my next epic.

Crafting wasn't an "exploit" per se, it was heavily unbalanced in the player's favor. Many aspects were unbalanced one way or the other, some of them were corrected, the rest will probably be corrected before beta ends.
I also fell into this trap I dug myself. Placed AP in speedy crafting, hunt for and upgraded my speedy crafters artifact. It's not that they are useless, I keep using the crafting strategy, only now the rewards are in line with the rest of the game.

@Tortmorgen

well, now you possess 2 great rare fodder artifacts!