What I've been questioning recently is whether spyglass is only useful for the quests that pertain to the event, not the entire event. For instance, the current event has quests that you need to do in order to get the 20 straitjackets. My theory is that the spyglass only helps with those quests, not the other collections that need to be done in order to complete the event. I may be wrong, but I just don't see a significant change in drop rates when using spyglass during an event.