These new potions that come with the event provide a new buff called hardy. This buff gives you an additional 100 HP.
When the event ends the majority of us will no longer have access to these potions as they will get used up.
Dupers will be able to keep an unlimited supply of them even after the event ends which gives them a real advantage over the rest of the server.
We have an issue with a clan of dupers on our server so I can see this becoming a real problem for us.