HUNTER ANY SPEC
best way to kill this guy in any spec as long as you have good dps.
1st: change all your pets to tanks
2nd: make sure you have a macro or something that allows you to misdirect to your pet easily and have it glyphed so it resets when you do it on your pet
/tar <pets name> for all pets then last put
now when you pull misdirect to your pet and make sure you do so whenever it resets so that youre pet is the target constantly. now the tricky part is when millie casts the Megafantastic Discombobumorphanator
when the cast is done or almost done, dismiss your pet before it dies then bring out your next tank, rinse and repeat. youll go through 4 pets before the enrage timer so youll need atleast 4 pets. when you switch pets he will be targeting you so bring out your pet and then feign death then misdirect your pet and carry on. by the time you have to change pets again your feign death cd should be up. it takes practice but is the easiest way ive found to do it. good luck