I find part of the problem has to do with nation sizes. Leaders with martial under 10, or with bad traits like craven, are much more prone to make major mistakes choosing terrible combat options, or get hesitant commander. But once you get limited crown authority to easily choose commanders, and a medium sized nation, it's easy to ensure that all your commanders are decent.
Super commanders with 20 martial and good traits for it don't seem that powerful, they're somewaht better, but not dramatically. Not like what a 6/6/6 leader can do in EU.
Partly this is because there isn't a stacking limit on combat; again like in eu3 where even if outnumbered, they only get 4 extra units of cav hitting you (and cannons, if any); without that superior numbers get to freely use their advantage, even in terrains like mountains where chokepoints are common.
Super commanders with 20 martial and good traits for it don't seem that powerful, they're somewaht better, but not dramatically. Not like what a 6/6/6 leader can do in EU.
Partly this is because there isn't a stacking limit on combat; again like in eu3 where even if outnumbered, they only get 4 extra units of cav hitting you (and cannons, if any); without that superior numbers get to freely use their advantage, even in terrains like mountains where chokepoints are common.