Nah you can skip the purify. Very few people actually farm t50 with poison.
This.
The most trouble you'd run into with poison would be Deadly Poison anyways, and unless they manage to play 6 within the first, oh, 8 turns I'd say even that's not that big of a threat. Chrysaora, Scorpions, Pufferfish and Arsenic are all taken care of by this deck. Dune Scorpion is still a threat, but I can only think of one person who would actually farm T50 with a deck like that anyways.