I suggest to change on "Melee Config" parameter oon Phantom Strike, that allows you to add a radious arc and as well add how many target will hit on the radius you select.
If i am correct , for exemple if i set
Skill target angle - 180
Skill target number - 5
That means if you use phantom strike it will affect at maximun 5 targets in 180º around you.
Unless im wrong, it should be what you looknig at.