After hiding it on your computer's iTunes you shouldn't need to do anything on your iPad and/or iPhone, it should hide the app from wherever you are using that account (you are using the same account on your computer and iPad/iPhone ?). When I tried it this morning in response to another thread, as I hid an app on my Mac's iTunes it disappeared within seconds from the Purchased tab in the App Store app on my iPad.
Try logging out of your account on your iPad by tapping on your id at the bottom of the Featured tab in the App Store app, close the App Store app via the iPad's taskbar, and then re-open the app and log back in and see if they still show in Purchased.