Is mining hardness really needed?
I know that this makes a difference as you can see here:
This changes the question mentioned above to:
Does the game need this change in improvement scaling?
What remains to be discussed:
Is this value important to mod authors so that removing it would break their mods? The Mining time would remain adjustable, but the factor of improvement from drill to drill would be the same for every ore-type.
An alternative solution would be to keep the property but let player know how long a miner takes to mine the ore. For example in the preview window when miners are placed.
Would you prefer to remove mining hardness or to get a preview of the mining time? Or maybe you have even more ideas?