I would have thought that 5 out of 7 is enough to strenuously pursue all options to ensure defects are fixed. It should not matter that 2 of 7 happen to be owned by the developer. The 5 of 7 would be acting in the best interests of the whole Owners Corporation, regardless of who happen to be owners at this particular moment.
I would be making sure the 5 of 7 all fully understand the importance of getting defects rectified now. Acting dispassionately in the interest of the OC is your duty, even if at a personal level you might get on just fine with your neighbour who happens to have been the developer.