If you're building a toxic/infect deck, have you considered running [[Fynn, the Fangbearer]] instead as your commander? Can't speak for how good it is in commander as I'm only familiar with brawl, but it's a lot more thematic and hopefully won't cause the table to pull out their strongest decks right away.
As for Atraxa, you could go with a poison control/stax deck like the other commenter mentioned. Try to get a poison or two on each opponent, then proliferate them to oblivion. I don't think it would be very effective though, and it might frustrate other casual players to play against a more controlling strategy.