I've never understood games having an 'assassin' class. An assassin is just somebody who deliberately targets and kills other people for political or financial reasons. (Or a member of a militant Persian Ismaili sect.) Why have a separate class with separate abilities?
Similarly, barbarians. 'Barbarian' is just a pejorative term for somebody from a technologically-backwards society. (Or a member of a certain invitation-only rugby union team.) Again, why have a separate class with separate abilities?
People who want to play barbarians or assassins should just pick a class and then give them a barbaric background or a prediliction for murder through background and flavour. For example, a mage who kills people for money: an assassin. A cleric from an isolated hill tribe: a barbarian.
These things have always bothered me. I think similar criticisms can be levelled at rangers, paladins and thieves, and I suppose by extension all classes. What is a fighter but somebody who concentrates on fighting? Or a wizard but somebody who concentrates on magic?
I propose that a line should be drawn in the sand: Is the class based around a special focus on a certain skill which it does better than all the other classes? For example, a fighter, mage or cleric? If so, it's on the right side of the line. If however it's just a flavour thing which is entirely based on background and/or personality (for example, assassin, barbarian, warlord), it is Bad and Stupid and Wrong and Not A Proper Class and should be cast into the abyss FOREVER!