"Boosted" Character has limited Access??

Nope, I have tried. Is there yet ANOTHER stupid Signature Quest I must do in order to fly in that stupid cave?
(unless one must enter a solo instance to get to the stupid merc?)

Echo Caverns is in fact designed for flying. There were some areas that seemed to be on the map, which I couldn't quite access while I was on the ground. Once I could fly, I realized what they were: shortcuts. Which was great, because I was definitely thinking it would take too long to fly from front to back in there, having to take the roundabout long route through all the areas. There are tunnels up near the ceiling, which allow you to skip from the front to the back. You can only access them by flying. Kind of a clever trick to gate access to them without needing any special scripting or anything. Just put them up high and out of reach!

I gained access to flight via the adventure signature quest.

Yeah, it seems it was another signature quest I had to do. And to be honest, lore-wise, it makes sense to limit the flying until you finish that quest. One of the reasons I didnt know about that quest line was that the npc giving the quest wasnt there to start with. You had to do atleast one quest in the area before he showed up. That threw me off. Usually you just go looking for the npc with the blueish quest icon.