That would depend on what kind of weapon you were using atm, you probably had a str based weapon while you were checking the description. Anyway this is a dagger skill, will only work when a dagger is equiped.

I have Daggers equipped and the skill description states attack scales with Strength as well

no

It really just depends! The fact it does piercing damage allows you to potentially one shot certain enemies that would rather cause problems over a few turns. Buffs to damage such as venom coating and firebrand also increase (and convert!) all of the damage to piercing damage. Very devastating skill in some cases. Also, a backstabber will likely take torturer anyway making the bleed always apply for a bit more free damage.

It does 100% damage + converts elemental damage to piercing + bleeding
So, damage with element on weapon is 105% + bleeding + venom coating + fire brand.

It's the mvp piercing damage because of backstab. Dual wielding backstab attack with this can KO enemies that are resistant to your main damage type or tanks that restore their armor often (e.g. bosses with high perseverance). And DOT is DOT. If you're aware of how much damage you need to spread around, bleeding can be a significant factor in getting a kill. Also worth mentioning blood factors into some great necromancy skills.