The Lord of the Rings Online™ Volume Two: Mines of Moria™ introduced many quests and deeds that are sets and sets of sets. What does Zubon mean by that, and why does he like it more for deeds than quests?
Take 2.5.5, in which you defend three places in Moria. You get one quest, and the goal of that quest is to complete three sub-quests. You now have four quests in your quest log, and as you complete the first three, it checks off the objectives on the frame quest.
Deeds work similarly but invisibly. When you finish all the deeds in a Moria instance, you are awarded a hidden deed and title for doing so. Hurray, you are a Curator of the Forgotten Treasury! There is a hidden deed for exploring all of Moria; you complete this by completing all the exploration deeds in Moria; you complete these by reaching all the exploration spots listed on those deeds. These are neat little bonuses, and I would like to see previous zones and instances retrofitted with them. But then, I like deeds, and getting deeds for getting deeds is meta-joy. (Was Annuminas the first of these hidden set deeds?)
Why are quests less successful? You can have as many deeds in progress as you like. Quests are more limited. Consider the quests for the six radiance instances. The Twenty-First Hall has two quests to go help people in those instances. Each of those quests is to go help several people with quests in those instances. Some of those quests are to help the person in multiple ways. The Grand Stair is the big one here: if you complete all the quests, you will receive more than half a gold piece in quest rewards because: Alice tells you to help Alice, Bob, Carl, and Dan; Alice wants you to fight fire orcs and their boss; Bob wants you to fight goblins and their bosses; Carl wants you to fight shadow orcs and their boss; Dan wants you to fight orcs and trolls, each of which is a pair of quests to fight them and their boss. All of that is one checkbox on the top-level quest to go help in the radiance instances. In a way, this is neat. In another way, good golly I need more quest space. I decided against seeing if I could cancel the top-level quests and pick them back up for insta-credit after completing the sub-quests.
But back to deeds, you get another quest slot for every 40 deeds you complete. More deed-hunting!