We are committed to keeping the world of Sanctuary a safe and fair place for all players, and our Game Security team constantly monitors for cheats and unauthorized modifications. All Diablo IV players agree to the Blizzard EULA as a condition of playing the game. The Blizzard EULA explicitly prohibits cheating, bots, hacks, and any other unauthorized software which automates, modifies, or otherwise interferes with the game. This is important to players’ security as well as the game’s long-term...
Overlay type of mods are always kind of critical because they simply work in a very similar way to map hacks and bots, using often the same type of functions. Even if it wouldn’t offer anything offensive it would still likely be something their anticheat systems catch as a positive.