The problem with making other guns insuperably better in their respective niches is that they are simply easier to use than the BR Pistol (edited because BR has always been easy and never should've replaced the CE Pistol). The aim assist on the AR in Reach was a joke (if the reticle was touching an enemy at all, the bullets would home in to the enemy, even if only the outer edge of the ring was over the target). The formula for success that worked so well in the first game was power weapons in their niches > utility weapon > power weapons outside their niches ≥ other weapons in their niches.
Having it work that way was successful because power weapons were undeniably the best in their intended range of use. The shotgun was a semi-auto death cannon at close range, the rocket launcher blew shit up hardcore, the sniper rifle was broken as shit like always excellent at all ranges but was undeniably the best weapon for long range. A suitably skilled pistol user could beat any of these weapons, but having the power weapon gave the upper hand. Other weapons like the AR and Plasma Rifle were the same to the Pistol. The person using the Pistol had the upper hand, but it was possible to beat it with anything (and not all that hard--there were several players who went professional in CE while only using AR instead of the much more common Pistol).
The problem here arises when the utility weapon has its utility removed. BR spread in Halo 3 and DMR bloom in Reach turned fights at mid range into random sprayfests where the outcome was all too often determined by RNG rather than player skill. It was a noble attempt to make the garbage weapons not garbage (the AR and its half a dozen or so clones), but they just can't keep any competitive integrity while making the W+M1 guns on par with the ones that require some semblance of aiming (although console controls and aim assist manages to dilute even that aspect ever since Halo 2 introduced online play). Many of the problems with utility weapons being "too strong" came as a result of poor map design. Too many open spaces and lack of alternative routes often meant that an entire team could have their access to the other side of the map completely shut off. Think Narrows or Orbital.
I've always stood by my belief that introducing RNG in an attempt to balance the game is one of the most effective ways of destroying the balance they might've had without it. There's a possibility that 343 learned from Bungie's mistakes and are implementing a way of disabling weapon spread/bloom in custom games, in which case I would actually consider picking up this game soon after release.
