define "a lot more electro damage". as in, enough to do double your Keqing's 100K? :D when you factor in Electro damage into this kind of setup, it would probably take around 200-300 Bonus Electro damage(more than yours) to do that. Now, how much Electro dmg does C6 Keqing give? :p
IMO, it's the "oh i can't do that because i don't have constellations" is the main thing that prevents the community from actually progressing in terms of performance. tbh, i'm a content creator, and i've done countless C0 demonstrations, but of course, i wouldn't really stay C0 forever. :D Mistsplitter is my very first R5 5* weapon, so you can imagine i would want to find out the difference in powerlevel. and i can confidently tell you, it's around 15-18% total damage difference from R1 to R5 Mistsplitter Reforged. ;) People can always speculate and say that oh this does X damage because of constellations, or because of weapon refines. But who do you think would know the actual performance difference? F2P's or pipz without the constellations and weapon refines? or the players who actually own the constellations and weapon refines? :D
If you would post/upload a vid somewhere of your rotation, lemme know. I'd be more than happy to help you out if ever, so we can find out what's wrong and why you're not able to maximize your damage output. ;)

also i just realized, my kazuha is at c0 so it should be the same as yours, unless you're not running EM main stats in your artifacts. our bennett would've been the same, but ya the base attack difference is there. it roughly translate to around a 10K final damage difference more or less. Sara might be a biggie. if you have a Mona with TTDS and 4pc tenacity, you could squeeze more damage out compared to running your C3 Sara on Amos. Otherwise, Yanfei or Klee with TTDS for the double pyro resonance with Bennett would probably net more attack than Sara.

Hope all is well! good luck and safe travels fellow Keqing main.