Tree of Savior

Having not actually played the game this is pure speculation but I think any class can technically be viable with how they set up skills to have such massive cooldowns and making a large portion of the game regular attacks. Squire in specific still seems to bring some exclusive party assistance skills as well

Balancing that many classes equally is -very- difficult, for example I think I heard someone already broke the game by using some ice wall technique where you break the wall in such a way that every single fragment hits the boss, instantly killing it.