Proliferate was introduced alongside infect as a way to give the mechanic more reach. The reminder text of proliferate even mentions players, so you're able to increase the number of counters on them
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Add two colorless mana to your mana pool for each card revealed this way
I personally wouldn't play them, as I feel the added consistency for our Cemeteries and Pit Keepers is more important, but in the end it's up to you
Whenever you draw a card, target opponent mills two cards
Id make sure to include cheap draw spells, like Frantic Search, Faithful Mending, and Meeting of Minds, to trigger our card effects on other players turns