Destiny has a very odd armor system, especially considering its shooter game play.
I would argue based upon the damage done by enemies and the style of play you generally have to conform to when attempting the harder content in this game, the only valuable thing about armor is the light amount, perks, and then the stats for game play tuning & min-maxing.
Understandably, the weapons you have in the game have a much larger impact on your performance (once you rule out light level (gear score) bonuses/penalties).
However the game design seems to hold helmets at a higher value level than the three other slots. For instance, crucible and vanguard purples are 65 marks per item for boots, chest, & gloves. The helmets cost 120 marks. While helmets generally have more desirable perks, I wouldn't consider them to be more valuable than some of the perks you can get on other gear (especially chest exotics). Then you have the raid purples, where the helmet can only be found in the hard raid, while it is required to have to hit 30 without an exotic helmet.
The way exotics are designed, with pretty much stats equivalent to purples with a bonus ability or perk to customize your game play along with your subclass & build, it doesn't make sense to me to hold helmets in such high regard. (Ignoring outlier guns that were either poorly designed or made to be OP)
I propose in future content that the helmet slot is normalized with the other 3 slots, and in turn normalize the gear check (light level) so that it is possible to reach the gear score listed by the game for the content without compromising on the customization of the exotic slot. With the 20% penalty per missing light level, its obviously you want to use it as a gear check for content, but at least let it be possible to hit that gear check score without having to beat said content already, if nothing else to provide a consistent and logical progression path.
-
Don't helmets make up most of the exotics? I hardly ever see exotic gauntlets (mostly on Titans) and not even sure if exotic boots even exist. I know for Titan there are 3 exotic helmets. At least 2 for hunter and warlock each. So it's easy to get an exotic helmet you like and really only need to choose between that and an exotic chestpiece. For which the chestpiece drops fairly often.