I'm not unhappy with the rules per se, it's just in this one particular case (a fighter with a really high CON) it seems that to not take an axe and use Brash Strike seems foolish, or, rather, to use a longsword instead of the axe seems foolish. In a game with so many viable choices it just causes a disconnect with me. I was hoping that someone with a better grasp of all the powers and weapons and their interactions could point out to me why longsword could still be viable. To put it another way, it would be clear that a fighter like this using a dagger as a primary weapon would be a bad choice. I just didn't realize that there would be so much difference in using a longsword vs. a battle axe.
As I understand it, granting the combat advantage with Brash Strike is going to cause me to take 10% more damage because I'll be hit 10% more often (not subtracting for the fact that my opponent would sometimes naturally have combat advantage over me). In exchange I'll be doing a little more than 4 extra hit points damage to my foe, although I'll be hitting 5% less often due to the difference in Proficiency bonuses for axe vs. longsword. So, I'll definitely be taking more damage, but my instinct tells me that, with the extra damage, I'll probably take out my foe a round earlier that with the longsword.
As for changing stats, I don't think retraining allows that. I'm willing to be corrected if I'm wrong, tho.
Thanks everyone for your input.