There are alot of soloable quest honestly... I believe almost all of them are atm honestly. AS well as all the leves.

Issue with a solo dungeons I see is balance, some classes will just be far better then others in it. So for some classes it will be a joke to beat others it will be nightmarishly hard.

That and Solo play does not show people you know your class in my opinion. It proves you can solo effectively, but in a group setting most those skills are usually worthless. In group situations the focus is working together balancing hate with dmg/cures apposed to knowing what to do alone which simply involves knowing what to do to survive longer then the opponent.