There’s a discussion going on over at IxDA about whether an interaction design can create great interaction without great visual design skills.
My answer is “It depends”. The two are overlapping areas and whilst some interactions are really helped or hindered by the visuals, it’s also possible to have something almost entirely visually driven or entirely interaction driven. In service design, the designed interactions are often human-to-human and have no designed visual element at all.
It also depends on who you are working with too. I remember reading Scorsese on Scorsese when I was studying film and being surprised and rather relieved that Scorsese’s storyboards for Taxi Driver were pretty much just stick men drawings and very rough sketches. Michael Chapman’s cinematography brought to life the miserable rain-soaked loneliness of late-night New York and Travis’s unstable life.