Slayer is an all around great class.
Great damage dealer (nice burst), lots of knockdowns + some stuns, decent mobility, and a prefect class for soloing.
Not much else to say.
Warrior is decent, but certain things are expected to be exceptional.
Does decent damage, but lacks in a lot of burst.
High mobility is one of this classes main features. While you may lack in burst, stuns + being quick help make up for it.
May have some issues in some cases when it comes to soloing, but its do able.
The big thing about warriors is they are able to tank. Tanking for them is all about not being hit. Plenty of skills to help with this, but a good tanking warrior isn't easy to come by.
The point is, warriors can tank and deal damage, but are not the best at either.