1st) we death guard auto-pass fear checks, so we have that going for us
2nd) Give your apothecaries the augury scanners so you can stall infiltrate and intercept
3rd) look into some grave wardens: for the same point cost of similarly equipped terminators you get better guns, amazing charge defense, and other stuff
Beyond that, without knowing his list for sure things that function well with
DG are: we can have allies + fortifications when we use the reaping, abuse this

, rad grenades WILL make him less comfy when it comes to charging. Against a "general"
NL list, I'd bring something like:
1 praetor (the reaping) w/ 10-man deathshroud squad
1 centurion (
MoS probably)
1 centurion (medicae)
2 20-man blobs
10-man
ML or other
HS squad
10-man
HS or support squad
1-2 mortis dread
3 apothecaries w/ artificer + augury scanners
10-man cataphractii (OR 10-man grave warden squad, would be
HS)
Ally in your OWN night lords for the
DS lolz (or robots/auxilia

)
Beyond that,
DG tend to do well against night lords are we are immune to their main buff (fear checks)