I don't know how useful this information is, but here you go anyway.
Level 47 Medic: 3 days, 21 hours, 47 minutes. First character made, so a lot of running around while learning may have slowed things down a bit. However, I solely play this character with my husband, Matt, so that may have sped things up a bit too.
Level 20 Esper: 19 hours, 28 minutes. Solo leveling character.
Level 15 Warrior: 8 hours, 37 minutes. Solo leveling character.
Level 13 Stalker: 7 hours, 33 minutes. Group leveling.
Level 9 Engineer: 3 hours, 38 minutes. Group leveling.
I rarely (if ever) complete entire zones.