While the "ease of flipping" category is, in large part, a product of the number of defense counters on the battle (battles range from three to seven defense counters, and a battle with three defense counters will be much easier to flip than one with seven), it also takes other factors into consideration, like whether the battle makes creatures (if so, we can use them to help defeat the battle, making it easier to flip) or whether the battle acts as removal (which can get a blocker out of the way, making it easier to attack and defeat the battle)
Tenuous Truce
Thats where Arabella, Abandoned Doll comes in
They are much higher variance than Sentinel, and while great cards, arent as essential as the rest of whats on the list especially since a good Sword of the Animist or Mask of Memory can fill those gaps quite nicely
This is a powerhouse
Being able to cast a 3- or 4-drop for free after playing this card is stronger than cascade, and we know how powerful that mechanic is