Q: Can I target the villain with Shield Toss if I am engaged with a minion that has Guard and defeat it using the same Shield Toss?

A: You cannot target the villain with Shield Toss if you are engaged with a Guard minion because the damage is dealt simultaneously. Melee works different because it is split into two effects that each deal 3 damage. -(Developer Ruling, Hall of Heroes)

Since its expected that (yet, not obligated) you will pay the Captain America's Shield back from your hand, the "real" base ER for this card is 2. Then we have:

• 3ER: 1x 4 Damage = \~1,3 DMG per ER
• 4ER: 2x 4 Damage = \~2,0 DMG per ER
• 5ER: 3x 4 Damage = \~2,4 DMG per ER
• 6ER: 4x 4 Damage = \~2,6 DMG per ER
• 7ER: 5x 4 Damage = \~2,85 DMG per ER

Some important considerations:

• You arent obligated to pay the shield thereafter, flexing 1ER for later turn. Super-Soldier Serum can also handle that 1ER.
• There must be different targets; this is a very limitant factor on low player count and or low minion density scenarios
• It starts at low ER per DMG ratio plus have diminishing returns
• Since its an attack with a value, it can be multi-increased with Aggressive Energy, Warrior Skill, etc.
• Can trigger Captain America's 4 dmg effect in team games with Winter Soldier or Falcon, even if they are just providing that card for you and nothing else. This converts Shield Toss into
• • 3ER: 2x 4 Damage = \~2,6 DMG per ER
• • 4ER: 3x 4 Damage = \~3,0 DMG per ER

Overall, this is a very bad attack card, per ER cost, with the sole exception of the abovementioned title (even with that is quite regular); its 0-Cost is a deceptiful nebwie trap, therefore this card should be used as your very last resource in critical cases where is imperative that you do that extra damage.