It seems to decrease with each World Tier.
Screenshots - https://imgur.com/a/I6pEtt3
8:59 pm starting time, 9:57 pm ending time
2369 Shards Starting, 2632 Shards ending
Total Shard Gain: 263. 1 hour of play time, WT2.
For comparison:
WT3 Helltide - about 120 Crystal
WT4 Helltide - about 60 Crystal