I'd be inclined to swap them out for a good set of Bilsteins regardless. I swapped to Bilsteins myself about 3 months ago and it made the world of difference to handling (for the better).
It *might* be the cause of your vibration but I'd be more inclined to point the finger at the tyres as others have suggested. I had a Hilux with 35" MTR's on it that looked perfect with 80% tread yet one of them just never would balance properly causing vibration - replaced the tyre and was fine thereafter

