I think i knew how they did it. i went and finish all available questlines on broken shores at the moment, complete 1 legion invasion on the broken isles, and complete 1 dungeon world quest on broken shore while command center building is active. Now my rep is at 8500+, only 3500 rep till revered. Since I did not make use of the darkmoon buff earlier, I have lost 10% of the rep gain. And I have never played the pet battle world quests, so there are lots of rep loss over past 2 weeks. If I have really done everything that is possibly done, I should be reaching flying rep now. Oh well, will need to farm world quests for a few more days.