3) I see a psychological aversion to the possibility of getting less than 25% because it's random. Players feeling this want an entirely deterministic mining mini-game, or at least feel 25% is too low for their comfort zone. Well... isn't the philosophy of Dwarf Fortress to go by the RNG, roguelike style? The community has adopted the "laugh as your dwarves meet their end in whatever messed up way" policy. It feels counter-intuitive that players can accept losing legendary[1] dwarves with rare 'perfect profiles'[2] to randomness[3], yet throw a tantrum at losing some rocks to randomness. Hmm, well I guess that's a dwarfy attitude in its own way.
Honestly, I tend to see this as an aversion to change, more generally.
As in, losing a legendary is something they've gotten used to, and know how to work around, so they don't complain, because that's just normal.
When something changes, and it forces them to change the old habits they've gotten used to, however, it causes complaints.
When new people start playing from this version onward, if there is ever any change from the current way things work, there are going to be complaints then, too, just as there were complaints when minerals went from relatively few in 40d to superabundant in early .31 to rare again in later .31, and then there was that worldgen setting that Toady added because of the backlash - the people who were used to 40d materials were fine with seeing the rare materials come back. The people who had only ever known early .31 and on saw it as some sort of in-game "punishment" that they would lose the ability to make "pyramids of solid gold".
The problem pops up every time there is a discussion about making mechanics more challenging in the game - the "megaproject construction only" crowd will oppose almost any change that will make the "simulationist" and "gamist" players happy because anything that adds more challenge or depth or complexity (in any combination) to the game they just see as a burden in their lego-fort-building program.