Blizzard has shutdown the Wintergrasp PvP throughout all realms while an unidentified issue is resolved. The Nitro Boots have also been disabled in Arenas while a satisfactory solution is found.
|We have shut off Wintergrasp on all realms while we investigate an issue which caused the games to reset prematurely. Thank you for your patience, and we will re-activate Wintergrasp once the issue has been resolved.—source.
After several attempts to balance the Nitro Boots ability in the arena, we have decided that we currently do not have an acceptable solution. Until we are able to better balance this ability it has been shut down in the arenas. We fully plan to continue working on this item and we intend to adjust it in upcoming patches.
We have plans to make certain that this item is still worth the investment made in it. So don’t vendor it just yet. source