I'm still new, my highest class is only level 21, but I can say that you can do up to 99 levequests a day (good luck getting through that many!) and they seem to recharge (I believe I heard) 4 leves every 12 hours. If you are getting bored from simple leve quests try switching to a crafter class and making some items for a while to mix it up. Other than that, maybe look for some people (I still haven't met anyone) because I hear it is a lot more fun completing objectives in groups than trying to solo everything! I mean, this is an MMO, so I suppose I should have grouped or at least talked with someone by now ;P As for a single healer class, there is a white mage job that you can unlock once you have a certain class at 30. Otherwise I'm still too new to know what the best tank/heal set-up is for groups. Best of luck, and happy adventuring!

~Zid