Tall but passable for human if needed, it was the power armor that mostly made them into the hulks they seem to be. My head cannon always leaned toward space marines only being about 6'4' to 6'8' on average. Especially for any kind a of recon which would be dead simple to set booby traps that take advantage of that while allowing normal humans to pass safely by not even knowing there were traps there. Though, I will admit that as much as I think the Primaris sculpts I have are great, scalewise I think they are a little much even for giant post-human power armor clad warrior monks. I don't think this will be too much of an issue so long as CSM can be fielded in larger numbers to maintain that threat.

The new CSM are noticeably smaller than Primaris. Fighting each other close up, it's going to be difficult to envisage the traitors as the threatening menace they ought to be, when the loyalists are a head taller than them. I have to say, I'm a little disappointed by this. So it seems that the new Primaris scale isn't being applied to Chaos Space Marines.

Chaos space marine chosen