P99 PVP code, dex and agility

[Danger]

So I understand that there is some sort of custom null code on red and green where in pvp an attackers dexterity and the defenders agility plays some sort of roll in hit chance.

Is it as simple as if the attacker dex > defenders agil a flat hit rate increase is applied or is it a scaling percentage?

Is the hit or miss rate so noticable it's worth pumping dex or agil? What idiosyncrasies have you found?