Heroes can generally ignore weak minions, but the beauty in hitting them a bunch of times is that even with an attack that only does 1 damage, the hero still has to roll to avoid the damage. A good hit might get them to burn gems on defense, and even a weak hit could get through if the armor roll comes up a bust.
But no, you don't combine them. They're wieners. They're supposed to miss and then get their heads chopped off.