[Kitriana]

Feel free to ask further specifics if i've not answered your question sufficiently.

First question:
So I'd say that experience for questing is a huge part of the game. As there is a balance set up through a mechanism of "brutality" that limits how much you can grow through combat in related proportionately to your quest experience. So you really have to do both.. quest (solving tasks, riddles, etc) on a solo or mostly solo basis and be involved in combat. If you ignore questing, then it will hamper your ability to grow through combat quickly at your brutality levels will hold you back.

You do get some general experience for exploring. But you get by far more through questing and combat.

Second question:

There is no necessity to die or reincarnate to join guilds or be useful in combat. Guild experience is achieved by practicing and improving guild abilities in and out of combat.