....got applied only on 1 arrow, so tell me, 1 vial of poison is usable only for 1 arrow - 1 sword swing? If thats really true then I am sad already..
As mentioned above one poison per strike.
However, perhaps oddly, you poison the bow not the arrow. That means you can apply the poison then switch arrow types and still use the poison. It follows the bow not the arrow.
I would not be sad. Poisons can be very powerful. You might only need one per strike. And they stack. So poison strike, then poison strike, could get you twice the effect.