You can definitely run Flooding off the mark- though any kind of quanta denial will mess you up. Not a bad idea but it would be definitely better as a rainbow so you can put some Sanctuaries and PAs and maybe some Druids for mutating water creatures into non water creatures. I don't see the point of the Chaos Seeds. Purify I can kinda see the point but I object to the card on principle. You don't need so many shields or Floodings.
I may try the slim version. But the fact is that in PvP1 and Bronze league there are lots of new players with their full 40-card decks, and that decks will lose by deckout pretty often. Being a 50 card deck I need those 6 Floods and 6 Shields, since both are needed for the ideal lockdown along with AM. I'd run it 60-card, but then it'd be too fat to be effective.
Also, Chaos Seed is to kill creatures with pesky abilities (like Devourers or FFQ's), some painfull water creatures, and also you get more chances of drawing your PC earlier (remembering the 50-card thing).
Purify is a filler card of the deck. I didn't use it the first 20 tries and the deck still worked like a charm, but you have 50 cards, so a couple of them won't hurt it that bad.