I still play it.
I started on Mia but went back to Lawolf cause it has more people and has more of an experienced community.
As for the game class classes that are under used would be the mages and acrobats, and knights.
The game is focused on 2nd job classes and not built on 1st job classes.
IMO if you are starting off new making a 1v1 BP or a 1v1 Blade is best. They level the fastest and easily make the most money.
They are more common in the game.
If you do want a class that powerful at leveling and least played Rangers (AoE archers) are your choice.