Will lens softness be apparent on DSLR video footage?
Your theory is correct, video is much less demanding of resolution than stills (1080p HD is only 2 megapixels). However you'll never get a truly sharp video image out of a Canon DSLR due to the strange interpolation/line-skipping that is used to produce a video frame from the full image sensor resolution, the result is always a lot softer than you would get from a dedicated HD video camera (or strangely the much cheaper m43 Panasonic GH2).