Yes, I've tested it in my game and that is exactly what's happening. The explosive resistance applies to both damage received and damage dealt, sadly. I'm running an explosives/engineering build and really want to be able toss a grenade at my feet! 🙂 Obsidian, could we pretty please get this issue addressed in the next hotfix/patch?
I tested it on my game. I can confirm that the armor appears to reduce my damage dealt by 90. Sorry I don't have recording but I could test it again if it helps.