Swords, plainly put, get way too much fucking ammo off of one drop in Crucible. With one heavy pickup, you can block a hail of machine gun fire or rocket, swingjump to some place you wouldn't normally be able to reach, then unleash your exotic sword special for a triple kill
and have enough energy left over to do it all again 3 more times. You can have your sword out and be getting kills the ENTIRE time between heavy. Difference between swords and the other heavy weapons is that they can drastically add to your survivability. Swords probably shouldn't even be allowed in skirmish lol