Having not played with archery too much on rng aside from staggers, anything I say is going to be 90% theory and 10% tested. That aside.
RR/GH/SD for any situation that would allow you to literally spam WSs. As you will usually get 2 ticks of regain per shot, its fully possible to 3 hit with this method - it saves you arrows, and greatly increases WS frequency.
RR/GH/stout arm. In situations where you are using rng on a top tier NM, and you cant spam WSs due to hate/tp feed/etc, this will give you the highest single WS dmg, and boost your individual shots a lot while actually building tp.
RR/GH/sanguine scythe. For slightly weaker NMs where pulling hate is less of an issue, and the NM doesn't have sky high def. The crit dmg boost from SS will up your single WS dmg and again your DoT by a great deal. The large enmity boost is a little unpleasent though.
Another possible atma would be Atma of the Burning Effigy. This is a major (30% or 40%) boost to WS damage for WSs with fire based SC properties. As arching is fusion based, it should work.
Furthermore for certain situations. Scorpion queen atma is 20stp and 10% crit rate.
I would recommend GH SS RR to start off with. You can play around with stout arm if you wish, but GH SS RR is a good combo for any RNG. Note that if you do use this combo, your crit damage is capped, so don't waste spots with things like loki's kaftan, crit dmg daggers, etc.
Afaik crit damage cap is now +100%, or at least much higher than before. Otherwise rng's native crit boost trait and RR would already cap.