Blast Suit

How does Private Vanguard’s ability interact with effects that modify how much attack damage a character takes, such as Blast Suit. [Source: WotC]

That ability doesn’t directly modify how much attack damage is being done to the character (note it doesn’t use “instead”), so it waits for effects like Blast Suit to apply, then sees if the character is taking more than 5 attack damage. If it is, the character takes 5 attack damage.

Let’s say I have a character with 10 health, 8 damage counters, and a Blast Suit. I also have Heroic Resolve face down. My opponent attacks, and my character would take 3 attack damage. What happens? [Source: WotC]

If there are multiple abilities trying to modify how much attack damage the upgraded character would take, the controller of that character decides what order to apply them in. In this example, you could choose either of the following:
Reveal Heroic Resolve first. Instead of taking 3 attack damage, your character is now taking 1 attack damage (enough to drop it to 1 health). Now Blast Suit applies, and the 1 attack damage becomes 0 attack damage, which is half of 1 rounded down. Your character ends up taking no attack damage and Blast Suit is scrapped.
Apply Blast Suit first. Instead of taking 3 attack damage, your character now is taking 1 attack damage, which is half of 3 rounded down. This isn’t enough attack damage to KO your character, so Heroic Resolve stays face down.

How does Even the Score interact with effects that modify how much attack damage a character takes, such as Blast Suit. [Source: WotC]

Even the Score doesn’t directly modify how much attack damage is being done to the character (note it doesn’t use “instead”), so it waits for effects like Blast Suit to apply, then sees if the character is taking more than enough attack damage to be KO’d.

How does Heroic Resolve with other effects that try to modify how much attack damage is done to a character? [Source: WotC]

If there are multiple abilities trying to modify how much attack damage the upgraded character would take, the controller of that character decides what order to apply them in. See the entry for Blast Suit for an example.

How does Lucky Vest interact with other effects that modify the amount of attack damage a character can take? [Source: WotC]

Lucky Vest doesn’t directly modify how much attack damage is being done to the character (note it doesn’t use “instead”), so it waits for effects like Blast Suit to apply, then sees if the character is taking more than 4 attack damage. If it is, the character takes 4 attack damage.

How does Autobot Whirl's ability to interact with other effects that modify the amount of attack damage a character can take? [Source: WotC]

That ability doesn't directly modify how much attack damage is being done to Autobot Whirl (note it doesn't use "instead"), so it waits for other effects (like Blast Suit) to apply, then sees if Autobot Whirl is taking more than 5 attack damage from a Ranged character's attack. If it is, Autobot Whirl takes 5 attack damage.