Most co-founders are not designers, and most new businesses do not need to have a full-time designer on staff. Design in itself will not help you successfully raise funds -- hard data will.
Investors see thousands of pitches annually, so they are so quick to spot a promising startup. I know that this startup is your "baby", but your startup is just another commodity to an investor. Commodity stands out by price (ROI), not by a shiny package (pitch deck design). Having seen hundreds of pitches and read even more, I can tell from my own experience that majority of startup founders fail to succinctly articulate that is the value proposition for their clients, what is their sustainable competitive advantage and how much money investors can expect to make. These are my entry level services: http://www.anagard.com/services/InvestorPitchImprovement.html

If you are completely confident with data, and if just want to convey the value visually, then a graphic designer can help you, as said by people on this thread.

Somewhat off topic: Design is important, but it's not a solution to everything. The best example is Jawbone fitness tracker: beautiful design and app, raised 6 times more money than its competitor FitBit, but captured only 19% of market share at the peak. Today, Jawbone is fending off creditors, and FitBit is planning IPO. Execution matters. If you are curios to learn more, I wrote a case study: http://wp.me/pj2e9-db