Right now, the Vethea biome is named "Arksiane", while the other dimensions' biomes are named after the dimensions' names. Should the Vethea biome be called "Vethea" for consistency, since "Arksiane" as a biome name doesn't feel right?

No. It was Vethea for a while, but Arksiane contributes more to the "mythology" of the dimension.