Requires;
Scroll of Resurrection
GM Ticket
Luck
*()* = Things I did that may have had an effect on this.
Pick the level 80 of the class that you want then open a ticket saying you clicked the wrong character to boost and log out before it gets answered. *(I leveled my 80 to 81, learned a few glyphs, and transmogged his gear)*
When the GM answers you thru the support system on the main World of Warcraft site they'll say they can change the class for you as long as the ticket was made within 72 hours of boosting the character. They'll ask for you to say the correct character name that you want boosted and what spec you want it to be as well as if you removed all the boa items/auctions form them. *(I accidentally had an auction up as well as a couple BOA's on the character)* The GM will also inform you that the "wrong" boosted character will be permanently deleted.
After I noticed I got a response an I followed the instructions the original GM it had been quit a few hours so I'm assuming there was a shift change. A different GM handled the rest of my ticket and boosted the 2nd 80 I chose, an either forgot to delete my 1st 80 or didn't see the previous criteria that the original GM stated.
I found this out on my own by chance and luck, so if it's a re-post get over it and let it get buried. Good luck if you try this.