More info is being compiled at this thread on Reddit.
http://redd.it/14m28b

To Test,

Choose Champion with no Masteries selected and attack a jungle monster.

Then quit, and try again this time with the butcher mastery (2 or one points doesn't seem to matter)

Notice how you are still doing the same damage to jungle Creeps.

Those in the reddit thread are reporting inability to do damage to lane minions

The reddit thread almost has posts that confirm that the mastery does not work on Jungle camps.

http://img580.imageshack.us/img580/2830/73811840.png

-61 damage to wraith with and without the mastery...and 63 to lane minions.

Currently testing this with sejuani.

With the mastery, my autoattack does 53 damage to the big wolf
without the mastery, damage is.. 53.

Started cloth/5 pots both times, same masteries apart from the 2 points in butchery, same runes.

Thanks for this post. I am aware of the thread in Reddit as well

@Dannamoth

Any Idea how soon this bug will be fixed?

So does it work yet?