The way we have addressed this in the design of several business applications is to have a set of domain experts who review all designs in detail. They are considered members of our design team none are computer experts or even use computers outside the work environment but they are experts in using similar software to do similar tasks in the business.
They are very good at helping us anticipate the potential irritations of our design, accelerators needed by expert users, and suggesting ideas for solutions. We continually test with novices to help balance out their biases and sometimes-wacky suggestions.
You have to be careful to pick the right people for the group otherwise you can get people who are looking to recreate the "way it is" and you should anticipate having to spend more time demoing and showing your "ideas" than you might in other design scenarios.