The skill-set required is interdisciplinary, covering diverse areas such as product design, cognitive psychology, information design, graphic design, user research, and statistical analysis. In the US, for example, many universities offer masters degree programs in areas such as Human Computer Interaction, Ergonomics, and Human Factors Engineering. But in India, no such education is available yet. Myths are rampant. And the excuse given for this is that users can always be trained.
Training is no excuse for poor design.
All interactive products intended for use by humans should be designed for usability. The purpose and focus of usability testing and the skill-set required are very different. A related myth is that usability engineering is mere color choice or screen design. Usability engineering is not screen painting. It is about product design.