For a proper Linear workflow in Fusion I can really recommend these two articles on setting up Fusion properly for Linear and setting up your footage. The site includes a sRGB and REC709 LUT which you can install for your viewer.
http://www.comp-fu.com/2012/02/linear-g ... in-fusion/
http://www.comp-fu.com/2012/03/linear-g ... on-part-2/
It's also important to be sure that Fusion interprets your footage correctly - especially if they're cineon or some Log format. Fusion assumes that DPX files are cineon log - even if they're not. You can easily change this in the actual Loader Node in the Format tab.
Generally if an image looks blown out or too dark or just plain weird in Fusion, you've got the wrong colourspace or gamma or log settings. They can either be corrected in the Loader Node of the footage under the Import or Format tabs or using the Gamut or ColorSpace tools.
Of course, once you're working in Linear, you need to have a proper LUT switched on in the Viewer.
Maybe some of this helps.