(6 cost, Fugueless) E2 FF 0 Cycles Svarog with E1 Mei + HMC + GallaGOAT

Never doubt the GallaGOAT. Also Coggers Mei still working great.
Actually now that I think about it, Firefly is once again getting assisted by Trotters for this MoC 12 performance, just like in her debut patch. Some things just never change.
0:00 Wave 1
1:27 Wave 2
3:28 Builds

SPD reqs: Firefly needs 167.4+ SPD, HMC needs 157.1+ SPD, Galla needs 158.4+ SPD, Mei just runs slow.
Though the damage is close, Firefly can kill Wave 1 without resetting her E2, so you can squeeze 1 extra Firefly turn out of Wave 2 if you need it.

As for cost, it's theoretically 5 cost with GOATed FF/HMC subs but ain't nobody got time for that. Also if you really wanna cost cut, Fugue makes E0 Fly able to 0 cycle, just saying.