One, the DNA evidence against Guede is for his lawyers to contest if they think it was collected, interpreted, or documented improperly. What I can say about the DNA forensics against Amanda and Raffaele is that the evidence was collected poorly in several instances, incorrectly interpreted, and undocumented. Again, the release of the electronic data files (which include the negative controls) is a near universal norm, but not in this case. Why not? If the work was done well, what are the authorities so afraid of?
Two, Guede did not live there, but Amanda did; therefore, there any DNA of Guede's found is evidence of his presence in the flat, almost certainly on 1 November (since there is no evidence that he was in the flat on any other day). Amanda's DNA is also evidence that she was in the flat, but she had a period of over a month in which to deposit it.
Three, the DNA evidence against Guede is secondary to the bloody palm print and similar in weight to the bloody shoe prints IMO. In other words it fills out the story, but it is not necessary to convict him. I have previously stated that every bit of evidence collected on 18 December should be at least taken at a discount, and this includes the evidence against Guede, on the basis that it was not collected in a timely manner (citation previously given).
Four, the lack of Amanda's or Raffaele's DNA on Meredith's wrists, etc. does not help the case that they participated in the assault (such as restraining her), especially given that Meredith's sweatshirt had Guede's DNA. There is some information in the literature on DNA transfer in domestic assault that can be read for background.
Five, with respect to gloves, a failure to change gloves can lead to mixed DNA, but it cannot make DNA appear out of thin air. This is one reason among several that the mixed DNA between Amanda and Meredith is not particularly incriminating.