Trebla:
It's max of 540 for the song's duration.
Dryads II is 7% with dmg cap 563 - 9sec recast - 3 ticks (18sec) Duration
You have to receive over 8043 dmg while the song is running to be over the dmg cap (7% of 8043 = 563)
If you normally twist 4 Songs you renew it after 15 sec (fastest would be 12 sec because recast is 9 sec)
-> if your mob is > 536 dps Dyrad is absobing less than 7% (8043dmg / 15sec)
I think 536 dps is a low group, bigger duo mob (with my equipment).
But you are right it depends, if your cleric is near the mob.