Hopefully this isn't overstepping the "this is not a tiering discussion" header of this thread, but I find it tough to imagine a metagame in which Shadow Tag Shanderaa is balanced. Dugtrio is able to see moderate use with below average stats solely because of its ability, which isn't even as good as Shadow Tag. Shanderaa is a fantastic pokemon in its own right, so the fact that it has Shadow Tag seems like it would push it absolutely over the top.
The most troubling part of this imo is that Shanderaa basically makes steel types without Shed Shell absolutely obsolete. Forretress, Scizor, Skarmory, knight bug/steel, grass/steel, Bronzong, and Metagross are all outsped, can't swith out, and are instantly KOed by any fire attack. This is a serious problem because these pokemon seem like the only answer to the megapowered dragons in gen V like Ononkusu, Sazando, chomp, mence etc. With Shanderaa able to easily do away with these pokemon, the dragons are going to rampage through teams.
Honestly the only thing I see keeping this thing remotely in check is the fact that Tyranitar for the most part spells instant death for it.