I was struck by an SUV while wearing a high-vis green vest and bright yellow helmet, while riding a bicycle on a sunny afternoon. The offending driver had the opportunity to see me from the front, side, and rear before plowing through me. The first thing the driver said was "I was distracted and did not see you". Up to this point that bike had no flashing light, the other bikes I rode did. I have no doubt rear and front flashing lights would have increased my chances of being seen.

I strongly suggest bicyclists wear high-visibility apparel, I do. I also strongly suggest bicyclists use rear and front facing lights in the flashing mode during daylight, I do.

As far as the OP's original question, DiNotte's 300R and 400R (daytime only) lights are bright enough for short & long distances, and off axis viewing. The Hotshot is only bright when viewed in a narrow line of sight channel (~15 degrees) for short distances in daylight. Evaluated in the bright enough for daylight context, the Hotshot is not enough.