Regarding the bubble head many mentioned, I will add my 2 cents about it:
I wouldn't call them too big, fugitive had his lower mandibles sag too low which made them cover the neck, which also made the illusion of the head just standing on shoulders making it look big, also his forehead/crest is at a different angle than the jungle hunter, his is more like wolf being more inclined towards front and making his head peak bigger. Also the more longer and "puffy" the dreads are, the more larger the head seams, add the never fully closing mouth which adds to size and we have the image of a big head.
But if U look at the scenes were he lays on the lab desk with his mouth closed (they used a different mild for the head, no animatronics) his head looks very proportional.
Wolf predator had the se problem, but his face anatomy was ok, only the crest angle being the selling point for "big head" look.
Berserker...yeah no excuse his head is too big, even for his towering phisique, I blame thea files being to long which made his face being too alongated.