Several of the ranged damage sets can't be slotted until lvl 27 (Thunderstrike and Devastation), so you may want to wait if either of those appeal to you. Decimation can be slotted at lvl 22 and is a good set. I would skip the Chance for BU piece and slot the Sudden Acceleration KB>KD. Slotting the entire Sudden Acceleration set is also an option. At a higher price, Overwhelming Force and Gladiator's Javelin are options, and Winter's Bite is a very pricy option. For the latter two, you'll want to substitute 1 piece for the Sudden Acceleration KB>KD.
Wormhole is an AoE foe teleport combined with disorient and knockback. The power targets a 20-foot radius AoE around a foe with a maximum of 16 foes affected. Wormhole’s pickup range is 80 feet. It doesn't require line of sight and can be used around corners. It also doesn't aggro any mobs it misses. Wormhole is a mag 4.1 teleport and will teleport bosses and elite bosses. After the teleport, Wormhole applies a mag 3 stun with an 18 second duration (with a 20% chance for an additional 1 mag) and a mag 15 knockback (you definitely want to slot a Sudden Acceleration KB>KD). Bosses won't be stunned when they exit, but they will be knocked down. I tend to follow Wormhole with Crushing Field so the stunned foes don't wander off. If you're playing on a team that's not familiar with Wormhole, you can put the exit point in the same location as the pickup point, or drop them on the tank.