I apologize for the delayed reply...Depending on the feature you're utilizing tool hub for should determine what machine it needs to be on. Depending on what you're looking to fix, you would need Tool hub local on each machine. 
Noted in the help article: "If the tool from the tool hub isn’t installed, it'll automatically download it in the background. It can take 2-3 minutes to complete. If you close out of the install, the tool may not run." -ProSeries Tool Hub: Helping you fix common problems and errors in ProSeries