Unless you had a gift/discipline/sphere/charm/artifact that said otherwise, str was the multiplier, and potence was unreal for auto damage.

[Skills help] finesse

Automatic

The abilities of the swashbuckler lie in the melding of tremendous skill
with balanced weapons that are capable of striking with great precision.
Finesse is the key to the swashbuckler's success as it provides him with
the edge he needs in several important areas.

Besides enhancing weapon accuracy, the skill also makes it more difficult
to parry and disarm the swashbuckler's dancing blades. Swashbucklers also
use finesse to make up for their lack of familiarity with other weapons
when disarming. But perhaps most important is the ability to find chinks
in the protection of even the heaviest armor. Just remember that for the
swashbuckler, not every sword is created equal - only certain finesse weapons
allow him to make full use of all his skills.

Finesse weapons: broadsword, curved dagger, cutlass, dagger, epee,
falchion, gladius, hunting knife, kris, kama, katana, khopesh, khukri,
longsword, machete, no-dachi, rapier, sai, scimitar, shortsword, sickle,
skinning knife, straight dagger, tanto, and wakizashi