Questing has come a long way from back when I started MMO's in the late 90s. However, this game isn't really doing anything revolutionary from what I've seen. Still plenty of run here, go there, fetch this, kill those and so on.
Dude, "questing" has changed since the notion of doing something for someone else. The post below has some good thoughts.
The key to the quests is how they are dressed up - ther is only so much yo can do with quests for progression, you need a lot of 'fluff' quests, the difference here is they actually put a lot of effort into fluff quests with a proper fleshed out story and reasoning behind it and with decisions and consequences in some cases. Really disguises what you are doing whereas a lot of games give a really lazy excuse to make you go kill 10 flamengos. Also the quests tend to involve a lot less running to point B, then back to A for hand in, followed by a quest at point B again - usually if a quest is going to keep you going back to an area, the quest giver actually spawns in that area once you do the first part.
It's little things like that which make a big ifference - in a lot of MMOs the travel time to and from the quest area often takes longer than the quest.
Regardless of the game type, there is only so much you can do in a game like this for quest types. It is how to dress them up. Quests can only be 1 of a few things.
1) Kill X things.
This is a combat quest. You either kill 1 or 50. The number doesn't matter. It could be pink fluffy bunnies or Vladamir the Ancient vampire lord. That is the fluff or window dressing. Obviously a game that only makes you kill 50 pink bunnies over and over again would get boring quickly.
2) Collect X things
This is to gather something. It could be related to combat in that only a certain enemy has the item that "drops" for a quest. It could be completely no combat. Such as picking stuff off the ground or "asking" other npcs for items. Or it could even be a crafting based quest where you "make" the thing that you are collecting.
3) Stand here
This is a "babysitting" quest. It can be combat related in that you guard an area from invaders, or just watch over an imaginary playground of kids for a set period of time.
4) Follow me
Escort quests. You basically are following around an npc or in some cases leading them around. Some may be combat oriented and they may not. This is one type of sight-seeing quest type.
5) Go over there
This is the other type of sight seeing quest. You are to check out areas. You either just enter an area, which could spawn a wave of monsters to fend off, or be forced to walk around a town talking to various npcs. You can be forced to see 1 location or many. The difference between this and number 4 is that you aren't dependent on having an npc being close to you during the sight-seeing our.
6) Solve for X
Puzzle quests. Basically you are forced to solve a brain teaser puzzle of some sort. Stacking blocks, playing angry birds, or doing algebra are all examples of this quest type.
That is it. Those are the basic building block principles to quests. There is literally nothing else you can do for quests building blocks. Everything else is just fluff on top and presentation. Most quests involve more than 1 of the basic building blocks to keep them interesting. To make quests fun and interesting it is a matter of how you weave the story around the basic quest building blocks to make the game fun. It's how you differentiate the quests and make them not seem to building blockish in nature. Many games never get beyond single building block, no real presentation style quests. They are literally, please go kill 50 bunnies because I don't like them kind of quests. Or they are please go gather 50 pieces of drift wood off that beach over there because I need them. There isn't much of a story progression involved and they are boring. What separates the good games from the bad ones is a good game takes those basic blocks and weave them into a storyline that makes them interesting to see the results of the story based on doing one or more of those questing blocks.