I'd say below 1k paragon mainstat is more important as it still provides enough profit.
You can't have too much AD but you can have not enough plain damage output. Best way to determine this is, before rolling go and hit a high GR. If your clearing time is bad but you basically just blast the RG, you should lookout for more AD. If you're melting everything but your RG fight takes 10 minutes, you have too much AD and too less direct damage.
If I can't decide whether to roll int>AD (WD here) I track RG fight duration with that idea in mind. If it's okay (assuming RG is not one of the impossible ones) then I'd go for better cleartimes (more AD).
The decision is more easy if that one item in consideration is ancient and you have a proper augment prepared (90+). That would minimize mainstat loss in a way that's worth it imho.