Technically, it's not a duo, SoP is watermark 
I tried several times to use SoP with dune scorpions and found it was not very efficient..
Also it seems the quanta will be a little stressed with the shards.
Technically, it is, because SoP is other and other doesn't count as an element
I'm not gonna add deathstalkers as well as nova's because I would need more quanta for deathstalkers (deathstalkers don't generate 2 new ones with SoR and dunes do and that makes the poison equal) ,and most of the time you'll have 1 pend and that's enough so nova's aren't needed.
In both cases it would become a trio