It's still early. Lots of people, like myself, are taking our heroes as much as possible because they need to be levelled up.
There aren't many PUGs in the endgame because the people who wanted to finish the game quickly are not willing to wait around for PUGs to form and take heroes, henchies, and guildies on their own accelerated pace. People who take their time and are willing to take the extra time to form PUGs simply haven't had enough time to get to the end yet. In time, more people will be in the endgame outposts to form more PUGs. The people who enjoy PUGs will continue to enjoy PUGs, even after heroes. Heroes are better than henches, but they can still be just as boring if you enjoy that human interaction aspect of the game.
Personally, I enjoy playing with others, whether it be guildies or PUGs. But, more important to me right now is levelling my heroes and getting the endgame greens to sell so I can afford to buy skills and signets of capture. I suspect soon, when i no longer need to build up my heroes and don't feel rushed by the high value of endgame greens, I will likely return to PUGs for going back through for any bonuses or helping guildies or whatever. Heroes will be used like henches - to fill in a specific when a decent human player can't be found.
Thank you ANet for the heroes. To those predicting the demise of PUGs - have faith - people will continue to play in PUGs. Once enough people get through enough of the game to provide a pool of people to group from.
M
