よくある問題My Outland Leatherworking won't level from 74 to 75.
Blizzard isn't aware of any bugs with Outland Leatherworking, but we're always on the lookout for new bugs.
In the meantime, keep at it - remember, as you approach the maximum skill level, the probability drops of an individual crafting resulting in a level increase. This can make that last one take many craftings.
The Game Master staff will not be able to provide that last skill level, but if you believe it isn't working correctly, please use the in-game bug report feature.