On the first day of the even I got my 60 shards from 10 boxes as expected. Since the daily reset on wednesday and thursday I’ve been getting either nothing or 1/5 shards randomly.
Earn Hellstone Shards from Hellcaller Chests dropped by Treasure Goblins and completing activities during the Greedy Emissary event, then exchange them at Hellhunter Baranar, located in The Foreground in Dornogal, for hellish armor sets and other goodies. Your first ten Hellcaller Chests weekly, across your Warband, will always yield Hellstone Shards. Hellcaller Chests can also contain Valorstones and otherworldly items.
10 chests per week per warband. Not daily.
You probably believed WowHead or other website misinformation.