Despite its poor reputation, the needler is probably the most efficient weapon to use against elites on Legendary. Although elites are great at ducking and dodging the AR, pistol, and PR, their AI fails miserably when trying to avoid a stream of needles. While a human opponent knows to run past the stream and cut sharply to exhaust the needles' turning radius, elites always do their normal strafe-and-duck routine. The needles can easily cope, and you're usually greeted by a couple of pink explosions. Sometimes an elite can manage to survive by getting behind a rock, but only if he does it very quickly. If he allows the needles to get too close, they will have no problem getting around the rock.
Here are a few tips for using the needler on Lengendary:
1. If your target is moving, keep the reticule locked on him. This makes sure the needles will track him.
2. Always fire an entire clip at an elite. Ammunition is plentiful.
3. Keep a pistol (naturally) for grunts and especially jackals. Using the needler on grunts is a lot of fun but overkill.
4. Don't be fooled by the reticule. The needler's range extends to targets that are too far away to turn the reticule red. Fire a whole clip at your unsuspecting target and watch as the needles 'notice' him and form into a hot pink string. An elite who is too far away to see you will usually not notice the needles until 90% of them are already attached to him.