It has a bizarre oversized chin look.
The Halo Wars rendition has the same issue.
Grenadier sans attachments is probably my favorite helmet from Reach. Clean, simple, generally well-proportioned without any weird business.
Nah.
I personally don't think the Mk V ever transitioned well out of Halo 1's original visuals. In some renditions it looks like a big cylinder, in some it looks out of place for being too plain, in some the details just come across as having a sort of odd plastic bubbliness to them.
Actually, I think the Chief's armor in Halo 4 might be the series' best attempt at porting the jet fighter tank aesthetic of the OG Mk V to a higher-fidelity visual style.