I am very late to this thread. But I am not too worried about the heart quests, solo personal story quests, and world events. None of those has anything to do with the game play itself. They are just quest delivery methods.
What I do worry about is the AI. I only played in the beginners areas, but it seems the mobs do nothing but zerg you. They don't dodge. They don't cripple or knock down. But once again is the beginning areas.
Like the OP said the party game play was what separated GW1 from other MMORPGs. With party game play there were cooperation and synergy. That seems to have been taken away in GW2 with a lack of partying. In the beginning areas, it seems we have humans zerging and AI zerging. There were a lot of players but teamwork was minimal.