Miners are great to get rid of some early threats to the fort but the most important skill is dodging and shield user imo.
After I have 40 dwarfs I'll start setting up a proper military with swordsdwarfs. I don't know why but swords seem to work best for me. With hammers and axes I have my dwarfs kicking, punching and biting all the time but they do make use of their swords.
If you are worried about strength and stuff: Just build 20 "dry" screw pumps in a room and give your entire military pump operator as their civilian job. 2 months training, two months pumping and two months in the danger room and they look like this in no time:
(The kills are mostly wild life atm. I have the squads training outside the fort, next to the entrance. Giant dingoes and alligators make for good practice and they don't get cave adaptation! =D )
The nice part is that I can just put everybody into the military. Even if they start out weak and with bad endurance the pumping will give them decent strength after a year or two. All males, gay and asexual dwarfs are recruited unless they have a really critical job. The women get all the jobs that don't put them (and their babies) in harms way: craftdarfs, miners, farmers, haulers, nobles... all women.
I'm training one squad of female marksdwarfs for beasts with syndromes or fire. It's a pain to get them to train with their crossbows though. They empty one quiver and then they go on a break or something.