I do not think your flash (or any other) is not strong enough for macro shots. Flash power becomes more needed with not so close subjects but for macro shooting most flashes (if not all) would suffice. Many photographers use video lights (not so powerfull as strobes) for macro succesfully .I have S&S YS-01 which is equivalent to S2000 and for macro I normally have to dial down power to avoid overexposure.
I would rather think that the flash light beam is not properly directed to subject or strobe not properly sycronized with the camera.
I think you're right with the strobe not being correctly synced with the camera. I faced the flash at the lens and the photos that come out don't know the strobe being lit at all. However, if I turn the strobe to the "max" setting, it seems to work. Facing the lens, it blinds the shot so everything is just white. However, facing a subject, it is getting lit appropriately. Is there something in the STTL setting that would have my flash going off prematurely?