Will depend on which character as some have custom scripts but for most of them if you set the 'View Range' parameter to a low value, say 1 then that should stop them. (0 actually means infinite range btw)
The firing rate is a weird one, the bigger the value the less often they should fire, but I don't think that has any effect on melee characters.
Been there, done that, got all the T-Shirts!
