Picks bad weapons??! Honestly I don't use picks for militias because it is practically cheating! They kill anything! Dismember with every blow, then cave-in the skull+ the ease of training up legendaries even without a danger room. I think against unarmored opponents picks are the second most effective weapon in the game (after axes).
Just ran arena tests, 5 dwarves per side, all iron armor, adequate in all combat skills except weapon skill (since I don't think you can add mining skill in arena) and pick vs major dwarf weapons (again all iron)
Axes beat picks,
Spears beat picks,
Picks beat swords
Picks beat hammers
Tried same experiment with one on one set up, including whips and maces
Axes beat picks
Spears beat picks
Swords beat picks
Whips beat picks
Picks beat hammers
Picks beat maces
Next experiment: unarmored competition, 5 dwarves per side, no skills, no armor, just the weapon (iron)
Axes still won, but picks beat every other weapon.
As such, in the hands of a totally unskilled user picks are at least as good as hammers, but generally speaking, since a pick user is really really easy to level up (dig out clay layer=10 legendaries in minutes), they should be much more effective than arena might indicate. As these limited tests suggest picks are less effective against armored shielded opponents than axes, swords or spears, but more effective against unarmored opponents than everything but axes