Arcane Terraformer was stuck with 30 essentia on each side and didn't spray those magical gas to the top. After I disabled Thaumcraft Fix it became normal.

Please make sure you are on the latest version of Thaumcraft fix. There were some issues in older versions with consuming vis from the aura.

This was actually a different Thaumcraft Fix issue than the one I thought it was in March, and has since been fixed in the latest version