Totally fully agree with the previous statements.
I rarely strayed from the battle rifle, carbine, DMR, and light rifle when I had the chance. There was little incentive to use anything else when they were available in such vast quantities in every encounter from close quarters to open field.
Honestly, I don't see much need for the light rifle. The Prometheans were created to suppress swarming Flood, not to counter foes implementing "proper" tactics. As such, I doubt the light rifle would prove much use to combat and infection forms. Using the battle rifle against the Flood in Halo 2 and Halo 3 was great when range was at your advantage, but the second that encounter turned into fisticuffs, you were asking to be overwhelmed. When there's little need for the Prometheans to have even created it [in canon], I don't see much reason to keep it around. Besides, this thing was just a pain in the ass to use.
The designated marksman rifle needs to take a fucking chill pill. Only bring it around when there's an encounter to necessitate a rifle with rapid-fire, medium-to-long range capabilities, coupled with minimal ammunition scattered on the map. Not everyone should be carrying these. The DMR may be a beast in multiplayer, but it made whole levels so insanely simple to navigate.
In AutomaticLand, I never had any incentive to use the assault rifle when the SAW was in play. None at all. I would love it if the MA5 had reasonable "do everything" qualities as we know it from other canon sources [and common sense].