The Needler is a fan-favorite weapon, and having been here since the beginning, is seen as a staple of the franchise on par with the Assault Rifle or the Warthog. But consistently throughout the Halo series, 343 and Bungie have failed to make this gun work within the sandbox (which I’ll spend the second and third paragraph talking about if you want to skip that and get straight to my proposal for how the gun should change). The primary issue being that the inherent characteristics of the weapon (inability for individual needles to kill (consistently), slow and sluggish projectile movement mid-air, full-auto fire mode combined with a relatively small magazine) make for something that’s very, very difficult to balance properly. What are the options here? You could give the Needler greater proficiency in Close Quarters through making the Needles turn and track more accurately, but that would create a fire-and-forget weapon entirely lacking required skill to use that would overpower every other weapon in its class. Alternatively, you could give it more range and increase the speed at which the Needles move through the air, but unfortunately that niche exactly has been filled by the Suppressor. Or, you could give it a larger magazine and a wider spread or rate of fire, decreasing the damage to compensate and effectively making it a Covenant equivalent to the SAW, but as proven with Halo 2’s Dual Wielding the Needler doesn’t improve its effectiveness at all, and only serves to create a weapon that appears overwhelming and hectic but can easily be four-shotted by anyone even remotely paying attention.
This is an issue that both 343 and Bungie were and are aware of, regardless of if they’ve publicly stated it or not. As far as evidence towards this claim, the proof is in the changes they’ve tried to make to the weapon. From CE to Halo 2, all weapons now dual wieldable (Pistol, Plasma Rifle, SMG (if you see it as the successor to the AR in the H2 sandbox)) were all nerfed from their CE counterparts to take Dual Wielding into account… except for the Needler. The Needler, being the only useless weapon in CE (ignoring the PC-exclusive Flamethrower), was in-fact buffed by giving it more aim assist and heightened tracking accuracy. Still, even under these circumstances, the Needler remained a weak weapon to use. In Halo 3, the Needler again represents the outlier amongst Dual Wieldable weapons, being the only gun that had this ability revoked. Instead, Bungie tried to buff its base stats to fix the weapon, through increasing damage, rate of fire, accuracy, and projectile speed. Despite definite improvements being made, the Needler remained an unused weapon within the sandbox. In Reach Bungie continued this approach and again attempted to tweak its base stats (granted only slightly, as they were nearing the Needler’s fine line and threshold of ‘absolutely underpowered’ to ‘incredibly overwhelming’) via an increase magazine size and increased damage dealt. Again, no success was made towards making the Needler a fitting weapon in the sandbox.
343, having inherited this problem from Bungie, tried their best to make the weapon work in their sandbox. 343 buffed the Needlers damage and returned its ability to super-combine through Shields, a trait that was lost in Reach due to the game’s gameplay mechanics surrounding shielding. Within Ordinance drops, the Needler was made to stand next to the SAW as if the two weapons were comparable, which I speculate 343 might have been trying to accomplish within Halo 4’s balancing. However, as most who’ve played Halo 4 know, even with Needlers being one of the primary requisition drops the game had to offer, its increased usage was only superficial, and often would be turned down for Speed Boosts or Grenades, demonstrating its low status on the sandbox pecking order. In Halo 5, the gun plays more-or-less the same as it did in Halo 4, having been effectively pushed out of a possible niche by the Suppressor (not blaming the Suppressor, as its actually a pretty smart gun design), assumedly being left on the wayside by 343 in an attempt to bottleneck their focus during development towards issues more pressing.
To put its faults simply, it is the most niche gun in the game. Since Halo 3, the Needler has been a gun that works decently (through its ability to occasionally out gun the BR, granted this is done with the Needler user losing all of their shields) in Medium Range ONLY. In Medium - Long Range engagements, and just Long Range engagements entirely, the Needler is useless the second the target is out of reticle range (which is far enough away for any precision weapon in the game to comfortably engage), and in Close Quarters its projectile turning radius of the Needler makes the weapon more hectic and stress inducing for its user than it does its target, again being out gunned by all other Full Auto weapons in the game. The Needler is exclusively useful at one range, and is unusable at all others. A DMR can somewhat be used in Close Quarters. A Storm Rifle can somewhat be used at Medium Range. An Assault Rifle can somewhat be used at Medium - Long Range. This cannot be said for the Needler in any capacity.