So wait, it's harder to make a good game than a mediocre one?

I joke because I love.

I have no doubt that longer, more involved quests would take longer to design and QA. What we're talking about is one of those quests taking the place of dozens of the other kind...so the time very well might equal out.

The coding aspect, I would imagine, is like anything else. It's a function of the tools available to the designers. If the company has spent time developing some clever tools that allow a quest designer to more easily implement complex quests...then it probably won't be quite as dangerous as you describe.

It sort of sounds like you're looking from the perspective of a game design that is all set up from the start for the short task-type quests...and then they try to put in big ones. I'm thinking if they start out with the intention of quests being longer, more complex, and few and far between, it would probably not be so bad.