I believe I've heard this issue referenced elsewhere but I don't recall the details.
As a GM, I would be inclined to rule that only damaging attacks that successfully overcome at least one of the minion's defenses (AC, Ref, Fort, Will) can "kill" it and that "auto-damage" would not. This goes hand-in-hand with the potential issue of things like "I pick up an apple and throw it at him...it hits? Okay, he's dead!" that don't really make sense. Sure, being hit by an apple hurts, but it's not going to instantly kill a minion...sorry...
I honestly don't know how that would positively/negatively affect minion play in 4e, but that's my gut instinct.
HARRY DRESDEN — WIZARD
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