Well, after playing this for a while, I would suggest a purify to get rid of poison.
Would it really save you? poison decks will keep poisoning you, unless they are 2- att scorps.
Well, poison has never killed me, but since this deck has a slow start, I often find myself getting quite a bit of poison counters (against poison decks) before being able to shut them down. This rarely kills me, but it does prevent my EM.
So I'm saying that if you would put anything in (which is not necessary), I would suggest a purify.