Protection Warrior Shield barrier

[Hastty]

Hello,

I would like to ask about protection warrior ability Shield Barrier on Mists of Pandaria, the ability says that amount absorbed by shield barrier icrease with attack power, i found this equasion on protection warrior forum : absorb = max(2 * (AP - Str * 2), Sta * 2.5) for shield barrier used with 60 rage. So it counts attack power which doesnt come from warrior strenght and stamina as well. My question is whether the amount absorbed by Shield Barrier depends on whichever of those 2 are bigger at the time ( either stamina or attack power that doesnt come from strenght) or on both at the time, so amount absorbed increase with both stamina and attack power ( from vengeance and battle shout, since only those increae your attack power and not strenght). If the shield barrier depends only on one of the stats ( AP or STAM), whichever is higher, than in almost every case shield barrier will solely benefit from your stamina ( if you have 40k stamina *2,5 =100k absorb), which seems to be really confusing after all the ability itself says " the amount absorbed increase with attack power", why it doesnt mention anything about stamina than...

Thanks for your answer.