Great idea on stats. What do you think about a combination of the two methods below:
Q u o t e: Dexterity:
Tier 1 - Starts at character base Dexterity: Each point put into dexterity affects chance to hit an enemy foe.
Tier 2 - Starts at 65 Dexterity: Each point put into dexterity affects the chance to avoid melee hits and the attack speed.
Additionally, the enhancement from tier 1 remain and now also yield even higher chance to hit an enemy foe per point of dexterity.
Tier 3 - Starts at 135 Dexterity: Each point you put into dexterity affects the chance to parry an melee attack using one or two weapons made of steel/metal/iron.
Additionally, the enhancements from tiers 1 and 2 remain, and the player is yielded an even higher chance to hit an enemy foe, and the chance to dodge melee hits and the attack speed are both also increased, per point of dexterity.
Tier 4 - Starts at 205 Dexterity: Each point put into dexterity now increases the armor of the character, and also transforms the chance to dodge melee attacks, into being able to dodge ranged piercing attacks as well (not magic).
Attack speed, parry speed, chance to hit is further increased per point of dexterity.
Tier 5 - Starts at 320 Dexterity: Each point put into dexterity now transforms the tier 3 ability to parry melee attacks, to parry ranged piercing attacks as well.(Low % per point of dex - countered by the chance to hit if you'd see it from a PvP perspective.)
Armor, attackspeed, chance to avoid melee/ranged hits and chance to hit an enemy foe are all further increased per point of dexterity.
And:
Q u o t e: Each point into Dex = +3def, +0.25% faster run and walk, +5 attack rateing, increase chance of blocking, +0.20% increase attack speed,
Each point into Str = +2% more dmg +0.05% phical resistance,0.1% faster block recovery, 0.2% faster hit recovery
Each point into Eng= +2.5 mana, 1% faster mana regen, 0.2% faster cast rate
Each point into Vit= +2 health, +0.2 replunish life, +1% stamina regen and +1 stamina
What I'd like to see is a scaled percent benefit of tier 1-5. So for the first 75 points in dexterity you'd still get a percent tier 2-5 benefit, but it would be small. For each point above 75 dexterity you'd get a larger tier 2 benefit per point, but still small tier 3-5 benefit. When or if you get to 320 dexterity you'd get a significant boost in tier 5 benefit per point.
Hope that makes sense. What I'm trying to get at is rewarding a player if they do go all out in one stat. But also making hybrid builds more interesting by giving you a small percent of the tier 5 bonus per point. Gradually increasing that bonus when you hit the next breakpoint in stats.
The OP's system might result in everyone maxing one stat and going halfway in a second stat because the tier 5 bonus is so powerful.