I'm just gonna paste a response I left in a similar thread.

I want to play with anyone, but I don't want to play with everyone. Once you create content that requires groups, you've essentially forced my back against the wall. This is doubly true when said content is one of the major pillars of your game.

Story content should be soloable or accessible with a partner NPC, but should be fairly challenging. The biggest reason that this wasn't the case originally is because DoH and DoL classes were allowed access to the main storyline, which watered down the difficulty curve immensely. Crafters and Gatherers should have their own "story tree" that plays to their strengths.

Naturally there should be some clear benefits to grouping for storyline quests(battle time rankings/leaderboards, access to better bonuses, better loot, etc.), but content where grouping should be required(or at least encouraged) should be peripheral things like mass PvE, PvP, player-run events like partying, NM hunting, etc.