First, Shaman can be cast with black mana, providing ramp and color fixing to non-green decks
Luckily, cards like Skyknight Vanguard, Legion Warboss, Fable of the Mirror-Breaker and The Restoration of Eiganjo are pretty decent at winning games by themselves, giving us a reasonable gameplan against opponents that have removal or counters for our combo pieces
Its not just a skill-testing card, but one that rewards a particular subset of skills to such a degree, its hard to really draw good comparisons
I expect that it will almost always be cast as a finisher, but it's interesting that you can also use it to make emergency blockers for a turn if needed -- though I'd be sweating if anyone was playing White (Descend Upon the Sinful) or Black (Toxic Deluge)
Theres something terrifying about a giant unfeeling tentacle monster with an insatiable appetite for entire planes