PvM Wise, slayer instruments increase the damage as well.
Bards do 36/48/60 (2x 120, 3x, 4x) vs Players with Despair and I think 32%/41%/50% with tribulation
Vs Monsters that goes to 54/72/90 base on despair
With slayer 108/144/180 on despair and 48%/61%/75% on trubulation
Which is just about 160 combined on the low end and 315 on the top end. Nothing to sneeze at.