The Needler feels very situational in this game. It's only real good in spaces your enemy can't move side to side very far, and you have to be at the right range for the needles to lock on. You don't get much ammo either. A few misses and you might end up only getting one kill with the thing.
The AR could have slightly better accuracy, IMO. It should be a capable mid range weapon.
The needler is good for getting the jump on people, and the AR is kind of a support weapon. They aren't overpowered, each one is more optimized for their respective situations than other weapons are, and vice versa.
"Knowledge speaks, but wisdom listens." GT: RAGEface14 (I DO NOT accept random requests)
Needler is fine. AR is a bit over powered from my experience. I never played Reach but in Halo 1 and 3 the AR was NEVER a one clip kill from full shield. I have full shield all the time and I'll get one-clipped from an AR. Happens like twice a game.