I'll come back and correct if the formulas are off.
But basically for tribulation, at 120 Discord, you're bonus damage will be 60%.
So if say you are in doom gauntlet and using tribulation on a dark father.
If an archer hits the DF for 200 damage. If you're tribulation procs, you will hit the dark father for an 60% of that damage, so 120 physical.
The chance you have to trigger that damage out at 120 musicianship I think would be around 80%. (I'll have to check the exact math)
You could also be up beside him fighting and triggering the damage yourself.
All damage from tribulation is attributed to the bard.
A curse, a corpse skin, a bless. All are dispellable buffs/debuffs. The only way to remove the bard buff is to interrupt the bard directly.
The abilities mana cost grows linearly though the bonuses apply on a less linear scale. 1 Person with 20+ extra HP and periodic healing, is a nice thing.
Two people, one person and a pet that is alot of gain for 2 mana.