Extenarator

[Urat]

7 Agi will net you a little over 3% more damage

3% TA and 3%DA will be roughly 3.5%



Houyi: ~2.7% (barring acc)
Justicar: ~4%

I'm sorry but where are you getting these values from, and how are you even able to state a static % increase in damage for a piece of gear with attack+? The % increase from justiciar's will be entirely based on how high the defense is of your opponent. If you've already capped the differentiation then +attack will do nothing for you at all, whereas +agi will always give more damage.