
OP card. As an first impression, Shed a Light seems to be similar as Exploit Weakness, and both have powerful effect but seems to be hard to play. However, in the game, reducing shroud value of the location is one of the main mechanism beginning with Flashlight, but reducing fight/evade value is not. In general, making 0 difficulty investigation is much easier than that of fight/evade.
Moreover, unlike Exploit Weakness, Shed a Light has good combo parts. We can play 2 Shed a Light (with Double, Double) at ONE investigation to discover total 5 clues (3 from here, 2 from any). We cannot play 2 Exploit Weakness at ONE fight/evade even aganist elite enemy because the second copy has no normal effect to replace which is already replaced by first one. In addition, auto-succcess guarantee you can trigger "succeed by (your )" abilites, such as Scavenging. With proper tool, you can trigger Scavenging robustly, regardless of your stat.
Here are some useful cards to reduce difficulty for investigation: