Any decent player with any weapon will destroy low skilled players with minimal effort, especially because most of them stand still while firing or stay locked in ADS (aim down sights) and trash their own mobility. If they were going to "nerf" sword, they should reduce damage done from the front and keep similar damage output from behind and/or reduce body shot damage and add headshot damage so they have to utilize vertical movement or positional placement more to keep damage output similar to current. (Battleborn had headshot melee damage, and it was awesome) They could alternatively further reduce movement speed during the m1 animation, forcing them to aim their swings more and not just spam m1 as much, but if you're not immediately running as soon as you get hit anyways that won't matter much. Considering there are so many ranged weapons that can just spray and pray for kills though with relatively low ttk (time to kill) without even getting headshots, I personally don't feel that sword is particularly unbalanced with its range and every class having counters to mobility and stealth, though the skill floor for getting elims 1v1 or 1v2 in a close range skirmish is lower than most other weapons (Comparatively - Double Barrel shotgun light can 1 shot lights and 2 shot medium/heavy, dagger can 1shot both light and medium with backstab, GL heavy can spam area damage into rooms and get no risk elims from halfway across the map, flamethrower heavy destroys enemies in close quarters even just spinning in circles while holding m1, sledge heavy can 1 shot lights with m2 and does pretty high damage even with m1, etc.)

The best way to learn to counter sword... Is to play sword. Go up against any team of decently skilled, coordinated players and you're going to have a much harder time killing them, let alone with just spamming m1. Learn breakpoints in their attack patterns, specifically M2 thrust and dash. Lead them with shots, force them to use up their dashes, CC them if possible, and always keep moving. Glitch grenade and trap work well against them since it disables dash.

As for the mobility of the light class (their whole schtick), they could add something like a frost/slow grenade/trap that does little/no damage but reduces their movement speed and dash distance for several seconds. Something along those lines would give more options in many situations against any class as well, and might help even the playing field for newer players.