What about Achilles, Olive, Timmy and helioskrill?
4 out of about 197 sets, and they're not everyone's tastes aesthetically. Additionally though, Achilles isn't earned by the individual and relies entirely on time being put in by over a hundred other players, while Olive and Timmy are arbitrarily given based on others' perceptions of if your forged creations are good enough.
I feel like Halo 5's armor was done in a very bad way. It doesn't feel related to skill or achievement, just time put in. You don't have to work hard, just work long. It's a grind, and unlike Reach's reasonable for the vast majority of sets, in order to get some of the rarer items in Halo 5, you're looking at hundreds or thousands of hours of just pure matchmaking grinding, OR paying real money which makes it even less of an achievement.
Halo 3 and 4 had it right, with some based on playtime(ranks), but the rest based on Campaign, Commendations, or Multiplayer Achievements. You could actively work towards which sets you wanted to earn in most cases, and in Halo 4, even most of the rank based armor, you could choose which specific sets to work for by choosing your specialization. Actually, I'd love to see a lot more armors able to be earned through the Campaign.
Nothing is earned from Halo 5's campaign. The only Campaign related items in Halo 5 aren't even earned from Halo 5 itself, and that's pretty pathetic.
One last point: because of the REQ system, they reduced armor to "head" and "body". Face it, that wasn't due to hardware limitations, it was because people would riot if they made every single obtainable piece separately earned from REQ packs. If they brought the old way back, they could have individually selected pieces that are unlocked together or in order as you progress through an objective.