Warrior and Paladin need 540 defense, up 50 points from the current cap (5 points per level). This however does not mean you will be uncrittable in your level 70 gear because the defense rating needed will be much higher due to the way the combat rating system works. At 70 around 2.4 defense rating is needed per point of defense but at level 80 I would guess this is going to be nearer 4.92 rating per point of defense.

This will mean although you only need to raise your defense by the same amount, 140 on top of the 400 trainable skill at level 80, you will need ~689 defense rating to achieve that rather than the ~332 you needed on level 70.