Full disclosure: I'm a nube. Been playing a week. (lvl 42, rank 17 mosaic).
I was getting slammed with poison decks over last couple of days.
Like you, I re-tooled my deck (MO) to add in purify cards to counter the poison.
- Queen of the Night (not bad - double duty: purify (ranged) and bleeding (melee) and 5 points & 7 prov.) Useful still if not facing poison deck.
- Crows Eye (Alchemy - 4 prov.) - Nearly useless. not bad effect with purify plus boost 3, but cluttered up my deck and it seems like it showed up in every draw. I was wasting mulligans trying to get more useful cards almost every round.
- Pellar - (4 pts. & 4 prov.) I don't have this one yet, but contemplating replacing Crows Eye with it. It gives a new "random" target for the SK decks and puts 4 pts. I haven't decided for sure yet. I may continue using Crows Eye but adjust strategy to keep Beast growing when it's not needed for poison control. Boost highest unit by 3 so Beast will add 2 at end of next round or two. (just a thought) This at least makes it reasonable to keep and play Crows Eye. (in games besides poison control)
I have had some success using strategy of playing for long first/second round (I played all cards in 1st hand today in one such game to win first round. Altered my entire gameplan, but it worked)
They kept wiping out my cards and I'd build them back up. I had to adapt my strategy in game, because I decided I needed to bleed their deck of as much of those poison cards as possible before round 3. I even used cards that disrupted my favorite end round combo to win round 1. I won round one then played all my trash cards in round 2 (saved 2 cards for last round). Even though they were way ahead in the round they had to keep playing cards, because they couldn't risk a couple big cards taking the round.
I was banking on my tall cards beating out there depleted deck in round 3 and it worked out. It was still touch and go with all of the "draw from the deck" cards they seemed to come up with, but it at least worked out in this instance.
As a nube, I'm not sure if I face the level of deck that you're contending with but the strategy seems to be working for me. For now anyway.
I'm having way more trouble drawing the cards that I want to use in round three. I'm almost afraid to discard anything in rounds one and two, because they seem to be the ones that show up in round 3. I'm experimenting now with using up thos cards in rounds one and two just to make sure they're buried before I get to 3 round draw. I'd welcome suggestions from you more experienced players with regard to Mulligans.