They would all exile a card from the graveyard at different points (enters, attacks, dies, etc.), then they would have a second ability that related to the exiled card
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
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
When I went to try to rank cards for Limited I found myself at a complete loss
"It was like, yeah, jump in line," Hartlin told CBC News
Two toughness is perfect because youre paying for the ability to damage it without killing it but not for extra toughness you dont want