With the release of Kullervo, I see potential in things like the Xoris/Tenet Livia, etc. Using Rauta to proc melee combo counter (as the Rauta increases melee combo per shot hit, stacking multishot = more pellets, more pellets = more combo counter), while having the Xoris/Tenet Livia, etc holstered. I was planning on using this on Gara. While it sounds good in my head, it's probably overshadowed by other things. Assuming if you're fast enough you could just use another weapon that has better riven disposition etc. But I generally don't use a combo build even though I know the potential is higher because I'm lazy with upkeep. Rauta would allow me to circumvent that.
I'd love to hear others thoughts on the idea.
EDIT: Did some very light testing. Zenistar is currently my best non-combo stat stick because of a Riven I have for it and I get about 21k~ for each cast after the first (For some reason the first cast is 32k~). The Xoris using a sub-optimal build (it only has one forma and I'm using Blood Rush to track combo counter) and Rauta to stack combo to 11x cap I was getting about 35k~ every cast. There's probably some inconsistency because of Primary Blade Charger.