Baldur's Gate : The Sword Coast Chronicles : NWN2 Persistent World

I noticed when both blinding strike and expose weakness are active at the same time blinding strike seems to take awhile to go off.

If I deactivate expose weakness it is applied on the first hit.

Not a bug, just how the game works. You can only trigger one On Hit weapon effect at a time, so you will fire one, then the next flurry will fire the other.