Me and friend finished up a run through all the MCC Campaigns on legendary to unlock the helioskrill armor but the armor is not given, the legend achievement is not unlocked, and the service record seems to be very inconsistent with its recognition of completion but when I boot up the game all levels are marked as done on legendary.
Unfortunately if you are after the Legend achievement, it is what counts on here on Halo Waypoint. It can be patchy and very annoying. Looking at your service record on here, only Halo 4 has been registered as being fully completed.
There is some good news though. The Bandanna skull and Scarab skull can be turned on to make the re-try of the missions a little easier. And Grunt Funeral skull is greatbat clearing corridors easily.