Straight out of the Ghosts of Saltmarsh comes the skeletal swarm. For Limited, the perfect bomb for the BG Morbid archetype, acting as both "self-sacrificing" creature fodder and eventual finisher. For Historic and Pioneer, something to test for the Jund sacrifice piles. For Commander, a consideration to expand into BG from mono-black for Skeleton tribal.
This is way too slow for Historic and Pioneer sacrifice piles. Sacrifice piles are looking to win by the time they get to 5 mana.
It's fine in Limited, not convinced it's a straight bomb. These types of cards have generally got worse over the years as everything else around them become more efficient. It provides inevitability in a long game that you will definitely win with this, and it's a permanent that they probably won't be able to interact with, but it's not a card that's really going to get you back into a game you're behind in as you will just be forced to chump with the tokens and not really get anywhere.
"you will just be forced to chump with the tokens"
you can't chump block with the tokens. They're tapped
They still untap eventually. That's one of the reason the card is so slow, if your opponent is playing like a 4 drop into a 5 drop, and you are playing a 5 drop that does nothing until your next turn, you can easily end up in position that you are never able to utilise the tokens. Where this shines is in a game of parity or one where you're ahead it will really hammer home your advantage, especially if you sacrificing things for a benefit elsewhere. That puts it below bomb level though, as true bombs imo are ones that can bring you back from behind, and I don't think this ever does that as it's just too slow to get to the board. Its upside is when it's good it's probably near unbeatable as most decks probably won't be able to interact with it at all, and once this hits the table you've got to be on the front foot real fast, as you will inevitably lose any long game with this in play if you aren't putting pressure on your opponent.