I just downloaded the DT with role suggestions and have some comments.
I have two guys, both of whom are legendary miners +5. They both started simultaneously and worked in the same burrow, going from 0 skill to legendary +0 in dirt, then moved to stone, and I watched them. I have to say, the most important thing (and possibly only thing) about a miner is agility. I've seen this several times. In the race to legendary, which is all that I would think is really worth caring about, a more agile miner will win by a mile, because they move more quickly between dig sites.
Here they are:
Kubukdatur Otungerib
Willpower 1,269 1,015
Strength 2,104 762
Toughness 1,552 1,414
Endurance 1,198 808
Spatial 879 2,267
Kinesthetic 433 1,051
Agility 818 1,397
You have to drill out about 15 11x11 rooms in order to hit legendary from zero. When the second guy hit legendary the first guy still had to dig out like four or five more rooms, so when the second guy had dug out 15 rooms, the other guy had dug out 10 or 11, I think closer to 10 actually. So the second guy was like 1.5x faster. The second guy was sent to dig stone while the other guy stayed in dirt, so the second guy slowed down and the other guy caught up quite a bit. Even so the second guy was 1500 experience ahead when the caravan arrived.
Unless spatial sense and kinesthetic sense are really that important, it's pretty obvious that agility wins here.
I have a snapshot taken at embark, and you rate the first guy at 60.5% and the second guy at 53.01%, even though the second guy was dramatically better.
I would weight agility massively higher in your system -- as is, you don't even include it as an attribute for a miner.