Also, regarding the dungeons, I still remember people complaining in the beginning how difficult the dungeons were in GW2. Now, because people have "practiced" them a lot, they are easy. WOW has gear checks so often you need to increase gear to get past certain points. GW2 is only a skill check so once you have learnt a boss it becomes trivial. The only way to get tougher fights is to have new fights and after a period of time, those will also become trivial. The only way to prolong that is to make gear count more or to have a "no one can fail" mentaility. Neither of these will fit into GW2 where a person should be able to skip 6 months come back and not have to suddenly "catch up".
Your last point is contradictory, BTW. You can't have exclusive content without it being exclusive.