Killing the headless horseman before level 85

This is my little guide how to kill the headless horseman before you hit level 85. (for example if you have a level 60/70pvp character or something like that)

1. Queue with your 85 and some friends for the headless horseman, make sure that your friend is the partyleader by checking the option at the dungeonfinder.
2. Leave the group and logg on your alt.
3. Your friend can invite your alt even if he is below level 85.
4. Port yourself into the dungeon by using the icon at the minimap
5. Simply let your group kill the headless horseman
6. Enjoy your achievment

p.s. You won't be able to get the extra reward, but it's a nice way to get a cool title with your alt.