I don't think that the LP was nerfed enough, but in some cases, I believe it should give slightly more LP. My idea is that each consecutive layer give 8-12 LP over the next layer per mining "tick", since in most cases each consecutive layer you proceed has a much higher strength*tool requirement to mine. Currently I can mine layer 1 rock for 3-4 hours at a time on one inventory of food and water, gaining roughly 250-300K LP an hour, because layer 1 is so absurdly easy. However, it's much harder for me to mine layer 3, and layer 4 rock, but when I do, I end up only getting 20-30K LP/hr and using two to three times as much food, and water.
Layer 1: 2-6 LP
Layer 2: 8-12 LP
Layer 3: 14-18 LP
Layer 4: 20-24 LP
Layer 5: 26-30 LP
Though I do realize that later on, when people have godly strength, mining Layers 4-5 will be extremely easy and used as layer 1 for gaining LP. But, coupled with a strength*tool Q rebalancing, and made so that the layers require a higher "overall" strength, should cut down the amount of time it takes for this to happen severely. Because this isn't the only thing that would give absurd LP at higher levels. Take a look at players with 300-400+ UA who wilderness spawn to kill every animal in sight, gaining upwards of 600K LP/hr. Or players mass producing Q40+ bronze to grind Bronze Platebodies en masse.
Like the bucket nerf this is mostly aimed to stop new (and old) players from making tons of characters with specific X amount of strength using X quality tool and immediately jumping into grinding 150-200K LP/hr with ease. Mining should be more rewarding for the progress you make.
This post has been edited, due to new information. LP rates rescaled.