I think, the Shards are not meant as elemental cards.
The Shard of Gratitude is meant as a "Thank you for donating".
The Shard of Divinity as special cards for Gods.
Thats the reason for the names.
And these cards should be won in normal games.
And if there werent as many shards in Top 50 as now, the Shards of Gratidude would be more rare.
It was not predictable , I think, that many of us have tons of Shards now.
Of course, the ideas above are really overpowered.