While I think the general idea of slowing ore progression for steel is a good one, I don't love the ore discovery requirement. Either you have iron ochre/bloodstone or you have to dig crazy far for it/trade for it once people already have steel. This requirement could make sense with perhaps more plentiful ore generation for the higher tier iron ores (perhaps more plentiful nodes that are smaller?) but as it stands, it kinda sucks feeling like I am basically required to go trade for the discoveries in order to progress further in the main grind of the game (minehole progression) to make steel.
I do feel this is one of those situations where as a player the best practice would be to make my good faith critique of this attempt at slowing ore progression, but leave it to the devs to think of a solution that works for them. I'm just not really having fun looking for specific iron ores that don't give me anything I don't already have other than the discoveries.
The same argument could be made for rock crystals, but I feel that there is significantly less content locked behind levels 7-9 than 5-6. Thoughts?