Jackhammer got only nerfed once. The reason for that was massive server lag as the jackhammer works as a world edit command. When too many use it in a relative fluent pace, the servers would just rip. It also happened, as Jackhammer alone was better than the combination of Explosive + Veinminer which only costs half of the tokens. In general the nerf was something good to rather balance it more than destroying it.