This is a working version (at pre patch DF) of the auto misdirect WA/Macro

Required Macro

- with key release on spells

showtooltip Misdirection

/click AutoTankMisdirect

-with key down on spells

showtooltip Misdirection

/click AutoTankMisdirect leftbutton 1

Change the macro spell to your class.

Another fix (thanks from comments below and The Hunt Discord)

It will hit the party tank or main tank (raid).

If no tanks are in the group then it will hit your pet.

With thanks to Ronnotter (comments) for the solution.