I'll definitely be starting a mage. Within that, I think it'd be helpful when soloing to have a pet along with you to keep the mob at range and keep your health happy. Therefore, I'll definitely be using a necromancer 1-50. Once the real pvp and raiding starts at level 50, then I'll probably focus more on a pure DPS class that could have more utility in a group, so that means pyromancer for me. What I found to be pretty cool under the pyromancer tree that I foresee being pretty powerful is an armor ability. It grants every fire spell you cast a 10% chance to reset the cooldown on your biggest, 6 second-cast nuke, and it makes the next cast of it INSTANT! As pyros already have some big DPS, when this thing procs, its GG.
I could also make a marks/ranger and utilize their range and movement speed bonuses to be a master hit and run person. Combined with either a Riftstalker's 15meter blink ability, or an Assasins stealth ability, they can do some serious kiting and hit-and-run, while still capable of soloing capably and putting out solid DPS for groups.