Regarding the tier system of attributes I don't believe that it is such a good idea.
If you implement this system you gotta be able to reach the last tier of the attribute and be able to put a couple points in it by the time you beat the game on normal. So it should be accessible by level 30.(assuming your around that level when u beat the game)
This means by level 40 to 50 you should be able to max out one tier, of one attribute (balance reasons you gotta cap a tier at some point say 10 or 20 points). So by max level 100 you'll be able to fully max two tiers, or go pretty deep in at least 3 tiers.
-only obvious choices which is the same as autostat
So at max level most characters will look the same. Unless you really want a str/dex wizard. So your not really adding that much characterization. But your adding a hell or a lot of balancing issues.
This all assumes you get 1 point a level. If you get 2 points you'll be able to have tier 5 in every attribute. Which isn't customization at all.
Attack? I got skeletons for that....