Is this supposed to happen?

This. If fairy rings are supposed to be extremely rare by default, then coming across 4 or 5 in the first plains biome I see is an issue with the mod's default settings. The config you cited seems to match up with the spawning behaviour I'm seeing, so I understand why it seems like my report is irrelevant but you are perfectly capable of checking Vazkii's twitter. Before making condescending comments like this please check every single square inch of the intended behaviour of a quark feature to determine whether the default setting is what it is supposed to be.