On certain legacy items, it's possible to have flat resource cost reduction for cluster arrow, which applies after the -x% rcr making it possible to reach 0 cost on your cluster arrow. In 2.0 you needed 3 legacy items to do it: Mara's, DML, SoJ. With Marauder set getting buffed through the roof and legendary gems being added, only having a double crit, socket Mara's was helpful (possibly only single digit of those are left, I only have one without socket)

With the addition of the resource cost reduction bow and not needing the sentry quiver with the new ring set, it's highly likely that these items will see a return. (Assuming the new ring set will be playable on DH)

PS: I know it's an old set with new bonus.

I did some math:
Cost = 40 (base) * 0.5 (bow) * 0.7 (cindercoat) * 0.7 (bounty reward helm) * 0.9 (paragon) * 0.92 (shoulders) = 8.11
So with only a -5 DML, we get 3.11 hatred per CA
With 5 base regen, ~1.3 from DML and +25% from hexing pants, we can support 2.5 attackspeed which is higher than what we get with bow, so we don't need to spend time doing anything else than cluster arrowing.
Of course we give up some dex and skill damage on quiver (and lack of being ancient).
I think it will be viable if non-legacy CA will be viable like it was before Marauder.

With attackspeed on weapon, rings, gloves, belt, bracers, we get 2.47 attacks per second. Might be pretty hard to manage stutter stepping for hexing pants but should be still managable.

legacy items are history...