Couple players told me that I should use justice pve 489 ilvl items and I will do more dps in raids and dungeons than with grevious, even though grevious 522 iLvl has every single stat better. Is that true? How can an item be stronger if it has lesser stats? And PvP power is allways an extra stat so I practically doesn't loose any mastery/crit/hit/haste in favor of PvP power.
(we exclude set bonuses since justice items are not set items and socket bonuses still don't make big enough difference)
Basically from my experience you will have less hit rating , since pvp gear dosn't contain that much hit rating , you would have to reforge everything in to hit in other to do something even then it wont be enough.
What Azoog said: get the valor and justice point trinkets and the rest can easily be 522 PvP gear, even better if you have 550 PvP gear. It is true you need to reforge a little to get the hit/exp cap but that should not be a problem. Also look if the gem bonuses on some items give you pvp power. If they do, just ignore the socket colors and put a gem that is best for your class.