Well the DMR pretty much restricts map movement on many maps, as you can just sit at one spot and kill people from all ranges. It also just blows all the other precision weapons away.
Solution: Take DMR out of loadout and put it as a weapon pickup on the map, like you could pick up a BR on Halo 3. This would also mean that the LightRifle would just become the new DMR, so take that out of loadout too; I say have a certain weapon set for different maps.
Like a UNSC loadout map would have DMRs, Snipers, Rockets, etc.
A Covenant loadout map would have Carbines(on the map, sadly, there is no super-long range Covenant precision weapon), Beam Rifles, Energy Swords, etc.
A Promethean loadout map would have LightRifles, boltshots, incineration cannons, etc.
A solution like this would avoid having to nerf the DMR and just having another weapon rise up and become the new “DMR” and also add some variety in multiplayer.