Wanted my hammer dude to be as tanky as possible so I went with high constitution along with evasion and dodge but they're supposedly useless once you get better armors? Isn't there a happy medium that utilize both armor and defensive skills?
They're don't become useless, but they (along with movement points) are reduced by your armor penalty. You can use the heaviest armor and also pump high Evasion and Dodge, maybe throw Nimble and crafting feats/materials that reduce armor penalty into the mix, but instead of enemies missing a lot, they'll only miss occasionally (with little or no Evasion or Dodge, they almost never miss).
Realistically, you should probably choose one or the other, and avoid anything heavier than tactical vests if relying mostly on Dodge and Evasion. That's the happy medium; maybe even riot armor with Nimble and fairly low armor penalty.
What, you want to wear a boulder and also dodge everything like a lynx? I bet you're one of those guys who like to dual-wield tower shields in fantasy RPGs.