Are you after a graphic designer OR someone with both 'amateur' graphic designers skills and tableau skills?
Sometimes it's hard to find a person with both skills but not impossible.
When creating infographic like dashboards, I normally get the design ready on PPT (*trust me it's a good layman wireframing tool), and do the actual work in tableau. The benefit of this is that you've already identified what you want in the dashboard without having to create too many views in Tableau (it can be draining when you don't know what you want). Next step, just create individual views that is to be placed in the infographic as per you design.
Try the above if you have an in-house developer. Might take some browsing the web for inspiration but with combination of floating objects, and containers you can achieve pixel perfect design in Tableau.
Happy to chat more if you need any help.