I work for a small company, and I am the only "Soft" IT person. I do all requirements, design, coding, testing (though someone always validates my testing), database design etc.
NEVER CUT CORNERS ON THE DESIGN STEPS - your end users will thank you. You will thank yourself too, because you WILL end up re-working it to make the end users happy. Even if your mockup is nothing more than a hand scribbled piece of paper, it gives them an idea of what to expect. Taking 10 minutes to scribble something out can save a week's work of time (been there, done that)
It also helps you in your coding. It gives you the chance to think about what you need to do, the most efficient way to accomplish it, and any obstacles that may be in the way.
For example, you may find that "simple" report you need to create is harder than you first thought because you aren't capturing some date on table xyz. It also broadens your horizons and shows your team, superiors, or even can be used for potential future career opportunities that you do more than the bare minimum and can get outside that box of "it's not my job" (<--- seriously, DON'T be that guy, we all hate him) or it gives you a chance for additional learning.