They create the visual layout of the interface from user requirements, keeping usability (and possibly accessibility) issues in mind while creating them; those layouts will be implemented later by developers. Instead of performing evaluations, they would benefit from having a way to search for good practices about some particular topic.
They have from average to good knowledge of usability (possibly accessibility too) principles although not as good as dedicated evaluators.
Context of use:
Instead of performing explicit evaluations, they will use heuristics (more usability than accessibility ones) as a reference when creating their designs.
They will probably need a way to search for guidelines regarding some particular aspect while developing and refining the designs.