Although the 2 for 1 can empty your hand rather quickly, formats like Legacy and Vintage are literally build on cards like Force of Will and would be absolutely unplayable without it
At first glance, buylists seem like horrible deals
Hosts of Mordor decks can use large Orc armies and powerful finishers like The Balrog of Moria to close out the game
UG Town Ramp In Blue and Green , youre looking to ramp up on both lands and card draw, to be able to keep generating value to find huge bombs that will eventually generate more value than your opponents can handle
Vivien's -5 can be critical against an Azorius, Bant, or Esper deck where landing a spell can be impossible, except for the anti-counterspell magic of sideboard staple Shifting Ceratops
Two toughness is perfect because youre paying for the ability to damage it without killing it but not for extra toughness you dont want