You say that your taskbar was broken even before applying the GPO? This is weird. As so far it seems in our cases that enabling it actually fixes the problem. We already had GPO with Disabled since last month and News widget hasn't appeared for anyone after June updates. But some users started to see distorted taskbar. Even though they don't have News widget.
So i assumed that something is not working correctly when widget is blocked by GPO (or registry) other than manually turning it off. You case suggests that it can still brake taskbar even if you don't block it.
Or maybe it brakes taskbar if widget was never active and it tries to get active, but GPO is already blocking it and some conflict happens.
Anyway, this is still a huge mess..