Paul Anderson used the word "heroic" because Scar was intended as more of an anti-hero.
But the faults with that Predator are not just that he has longer dreds and human eyes. The former wouldn't even be an issue.
It's the structure of the lower jaw, the texture of the skin is absolutely off. Even with the creative changes in place, the skin is just wrong. It looks like dry foam rubber. It lacks all of the moisture and leathery qualities of the first two Predators. The KNB guys made a few mistakes of their own, but that wasn't one of them. Their classic Predator looked a lot closer to proper.
This is what I was afraid of with ADI, unfortunately. They just don't know how to pull off the convincing skin, and knowing ADI I betcha the quills were simply eliminated because they were a pain in the ass (for some reason).