I must point out that soul wounds in Berserk, much like how Laciel mentioned, would render the afflicted part useless.
Dragonslayer doesn't negates durability, nor Regenerationn, neither does it kill with a scratch. However, what it does, if it does soul wounds just like how Slan's own attacks, is causing the wound always to re-open, no matter how you cure it, unless it is kept closed by some kind of soul-afflicting item or spell.
Let me explain it better: When Guts was cut through the chest by a soul-wound from Slan, the wound was continuously healed by both conventional and magical methods by his group, but no matter how hard they tried, the wound always re-opened. Schierke herself, a powerful - albeit really young - witch didn't manage to do anything but slow down the re-opening of the wound, and it was explicitly stated that the Berserker Armor was needed so Guts could survive.
Tl;dr: Soul wounds, in Berserk, will always re-open unless some kind of soul-afflicting power comes into play.
Idk if this was already discussed (Probably yes), but if the Dragonslayer works in terms similar to Slan's own, then I am 99% sure that it causes some weird kind of "wounding" status effect on the very least, negating Regenerationn to a certain degree at maximum.