What you've done so far looks impressive!! Kudos to you! Here's my feedback on the your tool. First I'll start out by saying though I have done a lot of modding, I've never before done any modding on quests so I don't know anything about them. I think the Quest Editor should be easy enough for a "Quest Idiot" like me to use it.
1> Because I know nothing about quests, I had a hard time understanding how to build them. The tool didn't help enough. The first quest I built didn't work in game anywhere close as I intended. The quest I wanted to build was very similar in structure to the Quest_RatsInTheRuins2 quest.
2> I think it would be helpful if the default view of the quest is something similar to the Order view that shows the overall layout of the quest. In conjunction with #3 below, some indicator (i.e. green check mark vs red X) to show which parts of the quest need more input and which are complete.
I hear you. I've debated over this for a long while. My first thought was to create a very basic quest wizard that would do as you said, however, the very first comments I got were I want to add this or how can I change that, which led me to making it more customizable and therefore more complicated. I think we could make a quest wizard that is very basic, but I wonder if that will have lasting power. I mean, honestly, it is not that hard to go into the xml and change the name of a quest and the monsters you fight to make a new quest exactly like the one you are modifying. I could automate that and maybe that is what people want. My thought was I needed to make a tutorial and then once people made a quest they would have enough experience to overcome the learning curve, and then they would appreciate all the options. Maybe not though.
The problem with me telling you what is required, is that I simply don't know in every circumstance. some quests require certain fields and some can be remarkably empty. It is very tough to tell what needs to be in the quest. I've sent out questions for the team, but I haven't heard back recently (something about being busy with the release I think
). So, what I would ask are what things would you want to change for a quest. Give me a list, like:
1 - title
2 - Picture of the quest
3 - Responses for the quest
4 - Description of the quest
5 - quest location (i.e. ruins, hut, etc.)
6 - reward for the quest
7 - monsters to fight for the quest
8 - requirements for certain options to show up
9 - rewards at intermediate stages of the quest
10 - pictures of the rewards
11 - item requirements for success
etc...
As you can see it starts getting big real quick, if we could really limit the list to 10 things you wanted to change. I think I could make a basic quest wizard, but anymore than that and you get back into the "advanced" editor you have now. And if you want to edit a quest you've already made, it becomes complicated again.
I'm open to making a basic quest wizard, but I guarantee that the first requests I'll get are to add more things you can change with it. 
Edit: I assume you know that you can already load existing quests and modify them, right? For example you can load the rats in the ruin quest and modify it all you want, and then save it to a new file (make sure you give it a new internal name too - just edit it in the save window before you save it).