Germany's three-time Olympic gold medallist was quickest in both runs in Latvia, to make it seven wins out of eight in men's singles World Cup events this term, his sole defeat coming in a sprint race.
In the overall World Cup standings, Loch is now 250 points clear of Ludwig with Fischnaller 44 points further back.
Russia's two-time Olympian was just five-thousandths of a second down on her German rival after the first run, but finished 0.052s in front to record her second win of the season.
Victoria Demchenko of Russia was third with Julia Taubitz, who has won five individual World Cup events in total this season, fourth.
Incredibly, this was Geisenberger's eighth runner-up placing in eight World Cup events - including sprints - since returning from childbirth, but she did extend her overall World Cup lead over Taubitz to 29 points.
Latvia also took third courtesy of Martins Bots and Roberts Plume.
Germany's reigning world champions and World Cup holders managed to get back on their sled, but ended up down in 22nd place and now trail Steu and Koller by 56 points in the overall standings.
Russian athletes took the mixed team relay with Ivanova, men's singles fifth Semen Pavlichenko and men's doubles fourth Vsevolod Kashkin and Konstantin Korshunov coming out on top from hosts Latvia.
Germany were third after a surprisingly slow lead-off leg from Geisenberger, while Austria were disqualified when PyeongChang team bronze medallist Madeleine Egle failed to hit the paddle hard enough to activate the start gate for Nico Gleirscher.
With just the Team Relay World Cup season finale at St Moritz to come, the Germans hold a comfortable 40-point lead over reigning World Cup champions Russia.
But the lugers will reconvene in Oberhof, Germany next weekend for a standard World Cup event followed by a standard/sprint doubleheader in Innsbruck a week later.