MM282:
Цитата
Minion: Minions are designed to serve as shock troops and
cannon fodder for other monsters (standard, elite, or solo).
Four minions are considered to be about the same as a
standard monster of their level. Minions are designed to
help fill out an encounter, but they go down quickly.
A minion is destroyed when it takes any amount of
damage. Damage from an attack or from a source that
doesn’t require an attack roll (such as the paladin’s divine
challenge or the fighter’s cleave) also destroys a minion.
However, if a minion is missed by an attack that normally
deals damage on a miss, it takes no damage.
Что характерно, cleave действительно косит миньонов автоматически.