Well normal-mapping still applies on these models, and afaik the doom 3 monsters were just lowpoly figures with heavy normal maps on them. sure they could have benefited from this technology as well. the back is supposed to be round but the silouette clearly gives away the lack of polys.
Also, it's worth thinking about how this would work on something like one of the giant monsters or mutants from a game like Doom3 for example - those things are not smooth curves separated by sharp edges, in fact it'd be a nightmare (pun unintended) to try and model something like a Doom3 demon zombie creature using these…