On my mint system all the files in /bin are 0755 except fusermount, mount, ping, ping6, and su, which are 04755.
0755 is a reasonable permission mask for a shared executable. Which executables are setuid will depend very much on your system's security policies.
Trying:
chmod -R 0755 /bin && chmod 04755 /bin/{{,fuser}mount,ping{,6},su}
(as root) can do little harm at this point (setting setuid root on anything is a potential vulnerability).
