More high fantasy-style magic users should deploy textile-based spells
Take control of someone's big Hydra or Eldrazi, do combat with them and then cast Fling as a cherry on top
Though that combo isn't quick enough to make Enduring Tenacity more than a bit player in Standard, it's the kind of card that life-gain and life-drain decks in EDH love to play with, as it's effectively a second copy of Sanguine Bond (albeit cheaper and slightly more vulnerable to exile-based removal)
In a big dragon deck, Scourge can often kill creatures or opponents, or it can even finish the game the moment it lands
The value of X is determined only once, as Intelligence Bobblehead's last ability resolves
For example, if you built an entire deck around specific cards, then it can be worthwhile to mulligan aggressively towards them