Wargame official designer DCalkosz on the reasons why the Great Druid was removed:
The reason Hamur was removed was because in the later stages, the card was too powerful, resulting in an outrageous lineup on the scene, and Hamur also gave great benefits to players who were already far ahead, exacerbating the imbalance.
And in some cases, this card can also spawn a full field of fusion monsters, but this is not the main reason to remove this card.
Overall, the card was removed, and the Fishman received the most impact.