He rolled with punches well, but was portrayed by press as guy who would take 3 shots to land one. Untrue, but it sold some fans on him. His reactions/reflexes were remarkable. Not type of thing that gets attention, but so important in boxing.
Absolutely, Marciano had good defense. He was a great duck and slipper, and very good at moving forward with aggressive counter punches off the slips. He could duck after punching and before punching. Hence, he was able to get close to his opponents despite being shorter and having a smaller reach, because he was confident enough in his defense to advance into their range while eluding their blows and firing away.