I recall the 1.5 GCD nerf was because of vs. rogue PvP and how they worked on Cata. I remember it had to do about how warrior could somehow counter some aspect and that allowed them to spam 1s OP's and kill the target. Then of course Blizzard gave us some stupid excuse like "different GCD's on warrior feel too akward anyway so it's better this way".
Too bad OP is so weak these days, that you couldn't kill a thing with it even with spamming it five times in a row on next patch. But I would take lower GCD over bigger OP damage anyway, because that would allow us to fit one slam on the rotation more easily...