I have noticed that a fair number of miners pick a rock until there's less than 5 chunks left, and then they don't waste the energy on that last go on a block. This means that a bunch of rocks are left around with only a couple chunks in them.
This is a jerk move on the part of these miners, but I don't expect everyone to change their behavior. Why spend 12 energy on 2 chunks when you can move on to the next rock and get 8? So my idea is the following:
* instead of rocks having 50 chunks with the last mining attempt yielding the leftovers, have a rock disappear after more than 45 chunks have been harvested from them. This might mean some rocks only give up 46 chunks, but others could end up yielding more than 50.