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

[Niwashi]

This becomes more obvious when you get past the 1st/2nd rank, and the accumulated experience for traveling around the world to kill various mobs nets you less than half of a single level by the time you are able to successfully down all of the listed monsters.

Are you just exaggerating, or did you get up into your mid 40's or so, realize you were behind, and then go back and do the 3rd and 4th ranks of hunting logs when you were way overleveled for them? Because on-level, they do much better than that. I just did the 4th rank of my CNJ hunting log the last couple days (at levels 38 and 39, so above the level of at least most of the mobs in that tier), and got a full level out of it, from near the beginning of 38 up to 40% of the way through 39.

The hunting log was designed to familiarize the player with the various maps and give them something to do that was more interesting/rewarding than side quests.

I'd agree with the first of those, but it was never intended to be more interesting or rewarding than sidequests. It's filler for when you don't have enough sidequests for your level, since there's very few sidequests in this game and they can only be done once, whereas you get a separate hunting log for every class you advance.

Class hunting logs are for classes, not jobs - hence the new jobs wouldn't have class hunting logs, since they don't have base classes.

By that logic, there would be no way to level the new jobs either, since jobs in this game do not earn XP. Only classes do. Of course, that really doesn't apply because the new "jobs" are in fact classes. SE decided they no longer liked separating them out, so they made this new hybrid version that's both a class and a job rolled into one.