DMR - It is overpowered, plain and simple. Between the BR, Lightrifle, Carbine, and DMR,the DMR has the fastest kill time, requires the least amount of shots, and can kill effectively at any range. The amount of shots required for a kill needs to be increased, its firing speed needs to be decreased, or it needs to receive a damage decrease at close range. I would be very interested to see statistics on global weapon usage, as I would bet a very large amount of money that the DMR is by far the most used weapon due to how effective it is. There is simply no reason to use any other loadout gun in the game, unless you want the weapon specific commendations.
Carbine - Underpowered, but not by much. Reducing the shots required to kill by one or two would go a long way to making this gun a viable choice. As it stands now, the Carbine will lose in a one on one against every other primary weapon if both players are of equal skill, so there is no reason to use it.
Assault Rifle, Storm Rifle, Suppressor - I find all of these weapons to be a little too weak. Yes, they are meant to be used only at close range, but 343's penchant for "medium to large" maps greatly limits their overall effectiveness. These guns are viable choices on the few small maps we have (Abandon, Skyline, Landfall), but on any other map it is almost always a better bet to use a DMR/BR. All of the medium maps (Haven, Solace, Monolith) have long sight-lines where the DMR/BR user has the definite advantage, and running an assault weapon loadout on the larger maps is suicide (unless you pick a spot and camp, a la the rock caves on Ragnorak or the center structure on Exile).
It is possible for both a DMR and a BR to kill a Spartan using an AR or Storm Rifle at close range if both players begin firing at the same time. I think that is ridiculous, as the assault weapons should be winning that contest every single time due to the specialized nature of the guns. I find that there is no real incentive to using any of the assault weapons in their current state, as a player can be equally as effective at close range with a BR/DMR and Boltshot combo while remaining effective at long range due to the BR/DMR. I am not asking for a range increase on any of the assault weapons, just a slight damage boost to give them a definite edge in close combat and therefore an actual reason to use them.
Boltshot - I do think the recent update applied a much needed nerf to the range of this weapon, but I still think the range needs to be decreased even further. Why not make the effective kill range almost nothing, allow the shot to pop shields at its current kill range, and up the damage on its single shots to allow for a quicker kill once the shields are down? The existence of the Boltshot eliminates any incentives a Scattershot or Shotgun would offer because the kill range is the same as both of those guns.
I have no complaints about any of the other weapons. I think 343 is doing a great job listening to the community, I absolutely loved the three maps we got with Majestic (mainly because running an assault weapon loadout was actually viable), and I look forward to what they have coming down the pipeline. Even with my criticisms, I think they knocked it out of the park with Halo 4 and actually exceeded the impossibly high expectations, so keep up the good work. And nerf the DMR. Please.