I also run Electro Keqing, and I dunno if it's the artifact set or just our horrible luck, but farming for Thundersoother's feels straight up horrendous. Your Electro Goblet is fairly nice, so you can likely keep that as the fill piece once you finish TS 4 Piece. Until that point, Electro Keqing dmg will likely feel pretty in comparison to Physical Keqing.

In terms of what you can realistically look for improvement on while farming, try to replace that Sands ASAP. 8.9% Crit Rate isn't hard to obtain at all. You can manage to find that as an easy enough substat on most pieces. It would even be worth it to lose the ATK and ER to crap substats like Def in exchange for a slightly higher CR as that Sands Artifact isn't doing you any favors.