Obviously, Slash also pairs well with the God of the Forge to give those long-standing mono-red burn decks yet another heavy hitter
(To proliferate, choose any number of permanents and/or players, then give each another counter of each kind already there.) The ability that causes Agent Frank Horrigan to have indestructible starts to apply as soon as it's declared as an attacker
If duplication gets more votes or the vote is tied, copy the spell
Well, it might be obvious to say free spells and fast mana, but theres not a huge amount of difference between a cEDH player dropping multiple rocks, and a casual player dropping a Sol Ring and a Jeskas Will with a Deflecting Swat in hand
On the other side of the coin, if this did improve Pox, that would be good for opposing decks like Delver, with cheap creatures, some burn spells, and Murktide Regent, possibly the best dragon in Magic, which can utilize that swollen graveyard