Then the Vampire was printed next, same cost, this time it adds flying and +1 toughness, but it just works once per turn so it's both better then Mentor (flying, bigger size, no mana needed) and worse (just once per turn)
Duel Links dont have the friendliest monetisation practices, nor the most fleshed-out esports scenes
On the other side of the coin, if this did improve Pox, that would be good for opposing decks like Delver, with cheap creatures, some burn spells, and Murktide Regent, possibly the best dragon in Magic, which can utilize that swollen graveyard
Significant print shift in manufacturing
In any case, the damage inflicted is so absurdly high that it can wipe out any Pokmon currently in the game in a single attack unless they use some Item, Pokmon Tool or Supporter that reduces the damage taken or increases maximum health