Oh man, so you basically have a story of 4 overpowered characters. That is absurdly tough for any series to make good fiction with just one Mega being, but with 4 of them I struggle to imagine how it would go right, if it is about story quality.
Art wise, it was well readable. I could tell what is going with few confusing exceptions.
Favorite thing so far were those 3 warriors, altough it was sad to see them plan so much to just get wrecked by Overlord without breaking a sweat.