To further complicate matters...
You have to take into account the differing benefits that classes get from agility. Warriors get different crit rating per agi from rogues, for example.
Also, individual specs may affect this. For example, as a subtlety rogue, Rhoach gets +15% to his agility (this applies to gear bonuses and buffs as well) so he gets a bit more than the average character from GoA. Also, he gets the same bonus to his attack power, except it's 10%. Seeing as how his agility boosts his attack power, he gets a double bonus (agility getting boosted, boosting his attack power more, which in turn gets an additional 10% boost).
Yay complicated!