Quote from FleckerMan
Going from 40% dodge to 55% is a massive increase in survivability (you take 1/4 less damage) compared to going from 10% dodge to 25% dodge (only 1/6 less damage), this is why it multiplies to stop the +15% dodge synergising massively with high pre-existing dodge chance. They really should make this clearer in the tooltip though... This change was patched in really early if I recall, and I agree that it is a good change, but tooltips don't make it clear.
Yeah i knew it made sence i multiplied. Its just the tooltip is very not accurate : p