I like where Halo 4 is going with this. Primary weapons that fill a definite niche, but can still overlap and can perform out of their comfort zones.
I also think that the DMR can be successful as a 4-shot weapon, with no bloom and such, since the BR is back.
This is what I think will happen.
DMR: Very Accurate, a bit slower rate than BR, very minimal recoil.
BR: Same accuracy and fire rate as Halo 3's BR, a noticeable, but predictable recoil.
AR: Accurate if shot correctly (Not spraying), strong recoil, but if most shots are put into the enemy, will definitely outshoot someone with a BR. So it'll take more skill to properly evade.
I never mind when someone that is good with an AR kills me when I mess up a four shot. It even pushes me to shoot with an AR, sometimes.