According to his theory the individual cells should continue struggling against each other for survival, so that only the fittest survive.
I think it a bit of a stretch to impute that view to Darwin.
If we understand that human evolution is in another stage where natural selection is not the most important factor, then it is cooperation with and protection of our fellow man rather than competition and the death of our fellow man that represents the forward direction in the evolution of man.
I'm inclined to disagree with this. Homo sapiens evolved as a social species, so cooperation with others in the group was always part of what constitutes human behavior. What we have really done, is change the cooperative group from a smallish tribe to all of humanity.
Don't we now protect the weaker members of the community? Look at what liberation it has brought us. Look at the variety of man. Have we not changed the rules of evolution ourselves? The use of glasses is a perfect example of how we are in the next stage of evolution. Just as individual cells have overcome their limitations with the technology of its community (think of the human eye), we have overcome the limitations of our biology and individual evolution with the technology of the community of man.
As you yourself say, "the driving force of evolution is always variation." What you describe amounts only to increasing the amount of variation that the gene pool can sustain. I tend to think of this as setting the stage for future evolution, but not as entering the "next stage."