I was doing Arena testing by having an armored dwarf get attacked by 10 simultaneous goblins with wooden spears to try to replicate the danger room when I couldn't help but notice how slowly he was gaining Dodge skill. Even when I'd start the dwarf with Proficient Dodger which is the highest you can have at Embark and the goblins have no spear skill which means they miss a lot, I never once saw the dwarf gain the next level in Dodge.
I eventually took control of the dwarf directly and discovered that only 3, yes THREE, experience points are gained per successful dodge. All other skills seem to gain plenty fast, but he'd have to dodge literally hundreds of times in order to go from even Novice to Adequate.
Surely this has got to be a typo in the code somewhere and a zero was left out of the total because it ought to be ten times more than that to make it more normal. A dwarven soldier would likely die of old age before he mastered dodging with only three points per dodge.
With parrying and shield blocking also being viable and easily trained options, this lack of dodging might not be such a big deal. However, Fortress Mode testing needs to be done to determine if this slow gain also transfers to Dodging Demonstrations as well. If so then this might be a big reason why organized training goes so slowly.