Players that had their dungeon difficulty set to Heroic previous to the patch will currently not be able to enter any instances. We are working on a fix and for now the workaround is to type the following:

/script SetDungeonDifficulty(1)

After doing this you and your party should be able to enter the normal level 1-60 dungeons again.

Sorry for the inconvenience.

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Q u o t e:


Yes, hunters arcane shot crits me for 1500, clearly a bug

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It's fine, learn to duck ;)