So i was using barrage while killing goraks, obv pretty bored and i start looking my runes and i notice somth weird.. it doesnt always cost any barrage runes to shoot barrage  idk why is that, sometimes u can hit like 3 times before it tooks runes, sometimes 1 times..

and other thing.. while i was shooting nechryeals with barrage death spawns didnt spawn when the nechryeals couldnt att me.

It's a feature! Higher level staves prevent runes. Staff level req / 2 is the preserve chance in %.