Toxicing Umbreon sounds like a horrible idea, since it just poisons you as well while it can carry Heal Bell. Porygon is also pressured horribly by Heracross, who can just Knock Off its Eviolite first if it doesn't want to KO with Close Combat. And Porygon NEVER wants to take a Knock Off, especially against CB Krook, who then 2HKOs with Earthquake when it switches out. Alternately, if you've already taken ~30%, you just get 2HKO'd by Knock Off after Rocks since, even though it no longer gets the item boost, it does 50% more damage anyway because you lost Eviolite. Not to poo-poo on other stuff P2 can do since it's a decent wall to other Pokemon, but it should never be eating a Knock Off unless you have absolutely no other alternative.