I used to think dodge is great perk when I started to play the game. I used to put it on every brother. However as I gained experience I was forced to reconsider.
Problem with dodge is that it is initiative based and problem with initiative is, that it depends on fatigue. Less fatigue you have, lover your initiative. On general level initiative gets low more armor, shields and weapons you put on, because all these things lower fatigue. In battle fatigue gets expended with everything you do. Even when enemy attacks you.
At the beginning of the game, dodge might seem useful, since your brothers wear little armor, crappy weapons and shields and battles don’t last long. However by the mid game, when you have 100-200 armors, heavier shields and weapons and battles last longer, you get very little from dodge.
Moreover increasing initiative won’t really help, since you need to invest 10 points in to initiative to get single point of defense from it (two if you count both melee and ranged defense).
Therefore the way I see it, dodge is very situational perk which can be used to complement some special builds like light nimble duelists or light nimble archers with lots of fatigue and high initiative. Problem is, game favors armor for protection, and you need very talented merc to make him durable enough with light protection. This mostly means very high melee defense to begin with.
And even with such special build, there are usually better perks to spend your limited quota.