The Light build I'd aim for is Shingen with Sniper Shot, Sol, Light Tsukuyomi, SSR Artemis, Michael. That gets you to the -DEF cap immediately, the -ATK cap after 9T, and gives you spike damage at the start of fights as well. It also effectively leverages the synergy between Shingen's HP weapon and Michael, making the team tankier while adding to its spike damage. Without SSR Artemis, you won't be hitting the -DEF cap without Mordred, Diana, or some other build with greatly reduced damage, though you can still reach -45% with Sniper Shot and Vine (after 8T). In short, SSR Artemis, together with Michael, enables effective damage builds for Light.

However, Raphael is still useful if you want to play the Overdrive delay game and run Black Propaganda instead of Sniper Shot. It's a valid alternative, but damage and mitigation will take longer to ramp up and won't peak as high. Which strategy is more effective will depend on the encounter.