I know quester quite well, and it's by my knowledge, a very complete and versatile plugin. Ragan69, the plugin's creator is quite the little coder, he coded the plugin to be able to interact with the majority of plugins there are.
This guide, approved by ragan and linked on his plugins' page was written by myself and explains how the version 0.63 works. The plugin is now in 0.7, so on some things, but not many, it's a bit outdated, it's still contains valuable information that might help you consider quester as your questing plugin.
Also, I've experience with it, and with standardized text formatting for writing up quests that fit multiplayer, if you're looking for staff for the developping of the quests, I can help. As Xenmai said, denizens can make quests but is more complex, quester is made for complex storytelling and is incredibly easy to use, in my opinion.
https://docs.google.com/file/d/0B-TYxWh8WaJ6eWlGUl9sb3c3c2M/edit
A little bit about this guide: it was written for the training of the staff of the server I used to be head content director for, so it mostly addresses the people there, and sometimes reference the server by name, I really don't mean for this post to be advertisement for it. That server isn't open, but it's standards for RP and the RPG feel are basically similar to HC's.
If you'd like to ask me questions about the plugin, don't hesistate to PM, or to ask me IG.