STR is really a threat stat. Yes it offers some passive parry avoidance, but as your math shows its not really a whole lot of parry.
But if your looking for avoidance from dodge then use dodge or def gems/chants. As for weapons, meh, the agi on ID is just icing on the cake really. Its the STR, STAM, and EXP that make it so sexy.
If your looking to up your threat, STR and Weapon Damage/DPS are the 2 best stats to upgrade.