Landing in vis. less then 550 m will require an autoland.
Landings in weather above 550 m. can be flown manually whereas a flight director is a great help during the approach , but also during the last -looking outside- part as you can have a quick glance at mainly your pitch bar for a bit of pitch reference in this poor handflown weather.
Nobody will use the flight director to flare or actually land though , if that is what you mean.
Again in the weather you prescribe , it is not allowed to make a manual landing(<RVR550).
By the way wonderbusdriver (in 737 upwards) you forgot (?) the :
DH 0 FT / RVR 75 m. (triple A/P).
cheers