Are router bit imperfections normal?
Just gas bubbles in the fillet brazing that joins the carbide to the shank. You can see the brass color of the brazing in the flute. The carbide is socketed into the shank and the braze weld in that area is the true strength element.

In brazed joints, the fillet is more cosmetic blending to reduce a stress riser than additional strength, the important part is hidden in the braze weld in the socket the carbide bit inserts into.