: FuD did it right by showing them sparingly, and making them hard to identify.
: FuD is also an example that Halo live-action can work.

Agreed. The Covenant were all in darkness, shade, and quite often surrounded by lots of motion that helped hide much of the seemingly unnaturalistic biological movement.

I dunno, maybe it's that in Nightfall, the gravity seem completely normal for all live action content, but the Elites still fee like they're... floating... sort of. Very smooth and hovery. I think some of the hues and shading aren't quite right within the environment just yet either. Hard to put a finger on the imperfectness. Uncanny valley effect :P

A couple of quick scenes were a little better in ep.1, otherwise they still just look like CG pasted on live action, so far.