FFXIAH.com

More exp from offensive ones, definately. I'm a campaign battle ***, so I generally jump from camp to camp, aiming for ones where we are on offense. (attacking forts, not just because of forts, but Fiendish Leechkeepers and lots of mobs, no waiting, etc). Battles seem to happen more often when on offense. I hate defending since NPCs usually own all of the mobs anyway c.c

http://wiki.ffxiclopedia.org/wiki/Campaign:_Experience_Point_Calculation_Guide#Level_Adjustments: Live it, learn it, love it.
(scroll up, my link has the bottom of the page for some reason lol)
Try to have a DD/Dnc or just Dnc as I see from your job, healing and damage together (while tanking for damage taken) nets loads of exp. Even as Blu/Whm I've gotten 5k+ from a single battle when tanking.

When you hit the end, you will just be asked to basically refresh it every 30 days to prevent expiration. It's annoying, I wish it would just stay, lol.