Obviously, the DMR is for Medium to Large Maps, and the BR is for small to medium maps. Currently, the DMR overpowers the BR because it kills faster, and is effective at all ranges, even in BR’s niche.
BR should be made 4 shot, and have it’s rate of fire slightly reduced. Without reducing it’s ROF, the kill time would be about 1.5 seconds. Instead, reducing it’s ROF should make it around 1.7 seconds. Only slightly faster than what it was.
DMR, should only get a rate of fire decrease, but not by a huge amount. Right now, it is about 1.7 seconds, so it is faster than the BR. However, nerf it so that it takes about 1.8 seconds at ALL ranges. The BR will beat the DMR, just barely, at close and mid range. But a BR will barely ever beat a DMR at long range.
The Carbine and LR should also get a slight buff. LR should have a slightly higher ROF, but you will be unscoped when hit. Carbine should have a damage increase so that it takes perhaps one less shot to kill.
For those that say gameplay speed would get slower, the kill times in previous halo games for these weapons was slower, and the game rolled just fine. Halo 3 was probably the pinnacle of multiplayer for Halo, and the kill times were not this fast.