Well, are we talking "class" only, or are you also including "subclasses"? Warrior by itself kind of overlaps abilities with some of the subclasses.
Warrior by itself is pretty necessary. It's the basic, introductory, default, plain-vanilla class. It is definitely a core class of the game. It may not be truly "unique", but it is fun, it fits, and is essential.
When we come to subclasses, any analysis will need to look at how they combine with their possible main classes. I doubt there is a case for the warrior to be removed, there may be a case for some of the more warrior oriented sub classes to be removed and features rolled into the warrior though.
