While the effect is purely luck-dependent, she can still be viable and even be overpowered
That being said, as u/CannedPrushka points out, it is still a little strange, all things considered
The Shadow Tag effect is a pre-existing condition on the Active Pokmon that was attacked by Wobbuffet
Because it is easy to get distorted if you line them up with the same sense as cards you normally search for, you want to consider them as a separate category

Japanese Pokmon Singles Buy Individual Cards products Jynx ex - 193/165 (193/165) - SV2a Pokemon Card 151 Holofoil Blastoise ex - 186/165 (186/165) - SV2a Pokemon Card 151 Holofoil Venusaur ex - 184/165 (184/165) - SV2a Pokemon Card 151 Holofoil Golem ex - 191/165 (191/165) - SV2a Pokemon Card 151 Holofoil Poliwhirl - 176/165 Art Rare SV2a: Pokemon Card 151 Ivysaur - 167/165 Art Rare SV2a: Pokemon Card 151 Charizard ex - 185/165 (185/165) - SV2a Pokemon Card 151 Holofoil Daisy's Help - 198/165 (198/165) - SV2a Pokemon Card 151 Holofoil Arbok ex - 187/165 (187/165) - SV2a Pokemon Card 151 Holofoil Basic Psychic Energy (210/165) - SV2a Pokemon Card 151 Holofoil Wartortle - 171/165 Art Rare SV2a: Pokemon Card 151 Blastoise ex - 009/165 Double Rare SV2a: Pokemon Card 151 Bill's Transfer - 199/165 (199/165) - SV2a Pokemon Card 151 Holofoil Entei - 213/190 (213/190) - SV4a Shiny Treasure ex Holofoil Zapdos ex - 194/165 (194/165) - SV2a Pokemon Card 151 Holofoil Wigglytuff ex - 189/165 (189/165) - SV2a Pokemon Card 151 Holofoil

This set will be revealed on October 10 at the New York ComicCon, but the most likely outcome is that it's based on Teenage Mutant Ninja Turtles