Is leveling broken in this game?

[Iscah]

Also with 1 class at max level you get an armory bonus

You don't need a class at max level. There's old information (still in the game) that there was a sliding scale of how much bonus you got depending on the difference between your current class and highest one, but even that has changed.

It's just a fixed bonus for any class that is not your current highest-leveled class. 100% for Lv1-70 and 50% for Lv71-80 if I remember correctly.