Double Yellows are the highest-HP 1-delay Double Bloons in the game. Because of this, it's a strong candidate for strategies involving Improved Fortification plus delay reductions, or OTK strategies involving multiple delay reductions.
Combining this card with Improved Fortification and either two Quick Ready or One Quick Ready and one Hastening Bloon, will guarantee that any opponent without shields, defenders, or Adora's passive will lose if there are no other bloons on the user's side.
Versus Adora when doing OTK strategies revolving a boosted Double Yellow, add Ability Ban to prevent her Sun Shield.
If the opponent has no Defenders, shields, or Adora's passive, three Quick Readys on each of the Storm's Double Yellows will OTK the opponent, even with Hero Protection active.
Amelia can use Double Yellow Bloons to feed her Act of Power to perform multiple Powers in a turn, particularly for OTK strategies involving Quick Ready and/or Double Trouble. Conveniently, two Yellows are exactly enough for one Act of Power.