Servers were merely up 20 minutes, but it was long enough for the players to find out that unopened Herald Rewards unintentionally contain Greater Artifact Belts.
After we outlined the issue in this post, the official message board erupted and the devs promised old rewards would contain old loot and only those (stronger) Heralds killed in Mod 6 would give Greater Artifact Belts. Not working as intended so far.
Looks like some people were smart enough to rely on the unreliability of the devs and will make decent ADs today.
Because this made live there might also be a chance that old overflow experience rewards contain the new, upgraded loot as well.
*** UPDATE *** As beckylunatic pointed out, the Overflow Experience Rewards are working correctly.