I've been playing this game for a while, and I can't find any good reason on how the game benefits from having the so called "ghost mining/running" technique. I'm fine with the soft time limit, but achieving great scores requires luring the ghost into gems, which, I think, it's not fun at all.
Ghost mining is not so difficult to execute when you are experienced in the game. It is just time consuming, and, for me, very boring. Removing this tactic would result in faster runs and preserving the fun. Without diamonds, that single pile of gold might make a difference in the leaderboards. Getting every treasure is difficult and fun. Waiting for the ghost, not so much.