@Pringlesman If I were you, I would just bite the bullet and fight my way to Hell LK. There it should be fairly easy to roll Shako rack. Up until that point, one extra skill point and whatever MF from the Tarnhelm wont do you that much good. And Shako > Tarnhelm, ofc. When you are playing through the game, it's better to focus on resistances and FCR, and not to care too much of your chars level. IMO it's best to get to Hell LK asap, since you can find most of the useful stuff from there.
That being said, it's probably a good idea to give NM LK few rolls. Like phar said, you can find Skullder's from there, and also Valkyrie Wing , which is hands down the best rack-runners helmet in the game. I stopped in Nightmare LK to rack Arreat's Face during my first playthrough. Also, the superchests in NM are also well worth it, you can already get great charms and useful runes, gems & jewelry while there.
[URL=http://www.directupload.net/file/u/50109/trk6e4ja_jpg.htm]
Google