Verbs can go pretty much anywhere. You'll find more often than not they appear at the end (whether or not it's the last word) of the sentence, but there is certainly no reason to say that the latin motto is incorrect. I will also add that when you have predicate nominatives (or adjectives) often (I'd hazard "usually" even) the form of the verb 'to be' (here 'est') is found in between the subject (here 'quisque') and the predicate (here 'barbarus'). It's not that you are wrong - your statement is correct, that latin usually has the verb at the end. But there are tons of exceptions and it can vary just by stylistic choices also. Keep learning latin though!