Consider the case of sickle-cell and thalassemia. These are two different mutations of one of the genes responsible for hemoglobin. Sickle-cell is found in equatorial Africa, and thalassemia around the Mediterranian.
If you have two copies of the sickle-cell gene, you have the disease sickle-cell anemia, and are much less likely to pass your genes on. Ditto for thalassemia.
But if you just have one copy of the gene, you have no ill effects. However, you are also resistant to malaria.
And so, in true Darwinian fashion, the genes are found in a large proportion of people in malarial zones, and are very rare elsewhere.
Are these mutations beneficial or not? The answer depends on how much malaria is in your environment.
And I will counter, this also implies ID at least as much as it implies TOE. After all, if you needed to reach in and write a hack that would meet a need in one environment and not another, it is there that it would be written. Actually, I cannot think of a case that appears to fit TOE that does not fit ID. The difference between us, I think, is that you believe the former is a theory and the latter is a faith. I assert that neither is a valid theory, and that both are faiths.
You really need to find some other argument for evolution. Any way you call it sickle cell anemia is not beneficial. It has not created anything which is beneficial in an organism. You need to create things to get from a bacteria to a human, an illness creates only destruction. And also let me note that many survive malaria without carrying this trait. In fact, if it was prevalent in any large amount of any population it would kill up to a quarter (that's called genetics, a well proven scientific fact) of the children of those carrying this trait. So yes, more people have survived without this trait than with it.