On Topic:Let us compare the vanilla (no skill creatures) of Darkness and Water
Black Dragon
10|5 for 10
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Ice Dragon
9|6 for 10
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(0<HP<6) is worth 0, (5<HP<8] is worth 1
From these stats we can conclude that the stats of Darkness and Water creatures are comparable.
Now let us compare the Infect creatures of each
Parasite
1|1
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:Infect for 2
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Toadfish
6|4
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:Inflate for 5
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The difference in Cost - Value between these two is 2
From these stats we can conclude either
Parasite needs a buff on the order of an equivalent of 2 attack or
Toadfish needs a nerf of the same magnitude or
Parasite needs a buff on the order of an equivalent of 1 attack and Toadfish needs a nerf of the same magnitude.
The Current side discussion:
A standard can and has been calculated. This standard can be used to balance the cards within the rounding necessary by the game.