It's pointless to continue stacking defense after you reach the 490 benchmark because other ratings increase far more rapidly than defense (15 dodge rating is .79% avoidance and 15 block rating is 1.9% block.)
If you're only going for uncrittable, you're right. If you're going for uncrushable, you're wrong:
Here are stats in order of contribution from fastest to slowest to bringing you toward making you uncrushable, posted with each stats equivalence to 1% uncrushability.
7.9 Block Rating = 1% Block
15 Defense Rating = 0.25% Miss, 0.25% Dodge, 0.25% Parry, 0.25% Block
18.9 Dodge Rating = 1% Dodge
22.4 Parry Rating = 1% Parry
25 Agility = 1% Dodge
7.9 Block Rating = 1% Block
15 Defense Rating = 0.25% Miss, 0.25% Dodge, 0.25% Parry, 0.25% Block
18.9 Dodge Rating = 1% Dodge
22.4 Parry Rating = 1% Parry
25 Agility = 1% Dodge
This post is faded because it has a negative score.