Hi David,
No, you do not need to install the SAP Screen Personas 3.0 to use the WEBGUI.
SAPKB74004 is quite old. Do you intend to upgrade to a more recent support package stack in the near future?
You can try updating the ITS handler class, by implementing for example, SAP Note 2163839. You don't need to set the parameter mentioned in the note, but only implement it via SNOTE.
I also would suggest to follow the steps from KBA 2234414 - making sure that the ITS MIMEs are correctly available to the web browser.
At last, delete the web browser cache and the server cache.
I hope this helps,
Cris