Multiplayer Perspective: I’ve been stuck debating how good this card is since its release. The most common arguments for it are Hero synergies (Spiderman, Spiderham, Drax) and enabling the usage of defense cards on your own turn. These are good reasons to use the card but I think this card’s true strength lies in accelerating build-out.
The perfect defense strategy revolves around flooding your board with lots of key upgrades that trigger effects on the villain’s turn (Electrostatic armor, Dauntless, Hard to Ignore). These upgrades are incredibly cheap and efficient but it can take a full deck cycle to get them all out on board. Taunt helps you hit them faster via drawing 3 cards and giving you a reason to flip down. Flipping down will give you access to even more resources accelerating build-out further. Using this play style I’d argue Taunt’s synergy extends beyond the select few hero abilities, to any hero with impactful Upgrades, Supports, and Alter-Ego abilities.