Very good point, Eoin. For those very reasons, my personal trade-off choice has been to go with readymade web site templates and customize them slightly. There are thousands of those on themeforest.net and other sites and the odds that you're going to use the same template used on another web site is actually relatively low (at least, in my experience).
Most responsive, one-page web sites look alike anyways and the truth is that most UI/UX designer will design whatever is currently trendy - i.e. looks more or less like website-next-door, not so much because they're lazy, but because that's what they are told to do by the startups they work for.
If you're referring to something other than public-facing web sites, then my comments might not necessarily apply.
In any case, a good book on the subject is UX for Lean Startups (http://www.amazon.com/UX-Lean-Startups-Experience-Research/dp/1449334911).
Generally, I agree with the "jack of all trades, master of none" theme several people have put forth here. Gifted designers have very different, and more "intuitive" skill sets, than developers who have more "logical" skill sets. As such, for breakthrough work, engage specialists.
A second point. You mention design and UX, but there is not mention of what is guiding the creative direction. Perhaps you have assumed there is a clear guiding brand direction before the design and development work is initiated. But in my experience, I see far too many companies jump into design and development without having a clear understanding of what their brand stands for first. As such, I'd suggest a 3-step approach:
1) Brand Definition - clearly define the brand first. What are the core values and key differentiators? Who is the target and what are their beliefs? What is your brand personality? Are you serious/easy-going, structured/flexible, formal/informal? What is your brand "tone and manner"? What types of words properly and uniquely represent the personality of your brand? This helps create your brand vocabulary which is critically important because it is the combination of words and visuals that communicate your brand to the visitors.
2) Design - given the brand definition, a creative designer can bring a brand to life visually in a PSD file. They will explore design concepts, shapes, and color palates that evoke the essence of the brand in a unique and engaging way. In addition, the complete brand can only be effectively communicated when the "design" and the copy or "Brand vocabulary" work together in harmony. As such, entrepreneurs need to spend as much time on the copy as they do on the design.
3) Implementation - here is where UX and web developers can determine the best way to implement the design created in step two. Again, somewhere in the process, there needs to be a great deal of focus on creating: clear, concise and compelling copy. The design attracts, the UX guides, and the copy converts.