I always do the quest in the morning, then in the evening i finish quest and go use the scroll.
When I don't have the time that day to farm with the scroll, then i finish the quest before i go to sleep, activate the scroll logout and start the next day with the scroll still active.
Then I do the daily quest with the scroll still active, or so something else with the scroll still on my buffbar.
Yeh you miss the 30% thingy but its better then nothing