Dragapult doesn't have a godly attack stat and in doubles Dragon Darts hits each opponent with a 50bp move, which is kinda weak . So is it worth using?
Short answer because I don't play doubles much, but yes, with STAB and Dragapult's high Attack stat, Dragon Darts has enough damage/utility to be useful in doubles. Here's smogon suggesting Dragapult with Dragon Darts in doubles: https://www.smogon.com/dex/ss/pokemon/dragapult/doubles/