It also depends on your camera settings. If you're shooting at f/10 or so, you're flash might be powerful enough. Also, shutter speed and ISO make a huge difference. Shutter speed will control the exposure of the stuff not hit by the flash, and ISO will change everything (same with aperture). Also, make sure you're not shooting faster than 1/200, because HSS reduces the output of that flash like woah.
I have a 5d3 and 430exii, and I have experienced zero problems with it, so I'm not really sure what to say other than what's already been said.