Bard is always a good choice to explore and learn with because they are so versatile, lots of people will ask for ranking help (go neutral so can group with anyone, probably human to lower exp penalty and have 23 charisma and no vulns) Lullaby and serenade are really great exploring songs, anthem and healing is good and you can do decent damage, so solo they can still explore most areas. Probably just as well as any char can, except mayeb transmuters once they get duo. I've done paladins and warriors as explorers, and sword spec dex based warrior with whispers is also a pretty good explore/learning character. Mage/communer mobs are a bit tougher but otherwise they do pretty well.