I remember when this game came out, there were several reviews posted about how it wasn't a game for solo players. I had managed to solo a few of the harbor dungeons before headstart even ended. I took a very long break from the game at one point, but when I came back recently, I've been amazed at how much fun it can be to solo in this game. I mainly play a paladin, and I've been able to solo virtually every harbor and market quest, many house quests, tangleroot, west threnal on hard, stormcleave on hard, VON1-4, and undoubtedly a ton of other stuff I'm not thinking of right now.
Last night, I managed to accomplish something I've wanted to do for a long time. I managed to SOLO TEMPEST SPINE! I'm pretty sure I'm not the first to ever do it, but it was still a great accomplishment for me. Here's a link detailing the adventure, as well as an extensive photo gallery:
I'd like to encourage anyone who hasn't really tried it much to give soloing a shot. The rewards may not be as great and quick as group play, but you can really slow down and enjoy the quests in your own way. I've gone through quests over a dozen times with a group, but never really knew it thoroughly until running through it solo and exploring everything. Plus you can actually stop and read the dialogue and enjoy the story of a quest at your own pace.
Group play certainly has it's advantages, and I probably group as much as I solo. But playing through a quest your own way with nobody else to worry about can really let you enjoy the game in a different way. And it helps you learn how to play the game far more effectively for when you do group.
Anyway, good luck in your adventures, whether you stand alone or group with others.