Some of you likely noticed that at the moment Divine Artifact Sets that drop from the Arena Chests are marked as Set (4) rather than Set (2). That is an error in the server data, one that has to be looked into and fixed. We are planning to do that as soon as we can.
Another important bug has come up as well, which is the Shield effects from these Artifact Sets not stacking with one another. I.e., if you have 3 Divine Sets equipped, you will only get 15% of HP Shield at the moment. We are aware of the situation and are working to fix that as soon as possible as well.
While it is doubtful many, if any, players managed to receive 4 Divine Artifacts of the same Set in just one reward drop, we felt it important to relay the message. Rest assured, we will be working on the bugfixes and rolling them out ASAP.