Well I have no statistics to back that up, but your talking dungeons which are all isntanced and your talking battlegrounds and sPvP and maybe WvWvW and end bosses they are in part instanced although on a larger scale but certainly the first 3, yes the end game entails a lot of adventuring there is no set direction you could play 100% without stepping foot in the instanced areas but at the end of the day, the dungeons have cosmetic gear you can only get in them and not from outside, and im pretty sure the same could be said of sPvP so if you choose to avoid instanced areas you'll be restricting yourself quite a bit but not to the degree of the regular mmos.
Nice for someone to say hello, most people just want me to bugger off :P