I was killing Lucidas and attempting the mini-boss on that map, I decided to run away and used Dark Sight only to be hit/bumped by the boss or a Lucida or something. I've used Dark Sight in similar situations where I have some aggro and non-aggro mobs around me and they usually don't/can't hit me once I enter Dark Sight so I don't understand what happened here. I don't know what hit me, a bump or projectile. EDIT: Annie whispered me saying it doesn't protect from projectile or magical but I'm not too sure it was that that hit me, I'm pretty sure I was bumped. Anyways, just to be sure maybe it should be looked into reproducing this just in case.
The lucidas and Eliza both have a magic attack, and in the screenshot you can see two or three of the lucidas using the magic attack. It looks like you were hit by it- which yes, it does hit through darksight (and always did in GMS)