If the electrical failure is severe enough to lose control authority, it seems just as likely that a hydraulic system would have failed. These planes are just too large to operate the controls mechanically, so in practice there is just as much to fail in a hydraulic system as electrical control, since both require power.

>>And in case of the electrical system being down

That is what the RAT is for, alternative electrical power. If the entire electrical system is down, ie electrons no longer flow anywhere anyhow, then everyone is doomed. But that is up there with the tail falling off. The are no backups for the wings/tail either.