Broken Illusioner hitboxes

What i expected was:

1.Summon an Illusion Illager
2. Kill'em with bow and sword
3. They split on the first hit
4. Hit them after i found them

What i get is
1. Summon an Illusion Illager
2. Kill'em with bow and arrow
3. They split on the first hit
4.Hit all of them but none damaged with bow and sword