Thanks for sticking with it. Auto hire wasn't broken as such, it only ever hired creel carriers and hardly ever fired. Now it hires the best value hauler while stone piles up, and the row flashes +1 when it does. The heave now pays 5% of the stone's price on a perfect pull, so it stays worth doing late on. And you were right about the cairn: quarrying was the bottleneck, so it barely helped. It now speeds up quarrying as well, so it's always a clear gain.