Class Hunting Logs are inefficient EXP gains. Amongst other issues..

[kazeandi]

The Hunting Log is amazing for lower levels, boosting your way to 15 as swiftly as possible, and it's very easy to complete the first two logs. The experience it yields does fall off hard later on, but it's still good filler if you're in queue or something

If I want a class to 15, I ask a FC mate and 20 min later it's done.