All hail Emperor Anet, and their new clothes!
Consent.
First ask yourself how many hours of enjoyment did my purchase give me?
If you have played over 60hr then, in my opinion you shouldnt be entitled to a refund.
If they change something you dont like, you stop playing and dont buy more gems/expansions not by requesting a refund because they added a hair color you disliked(extreme example).
In case you missed the point, ANet changes things to improve them.