I do agree with this! There's a fair amount of space nearby that could have been utilised; enclosures for both species don't require too much space.To be completely honest again think perhaps that area where the visitors path is and the Fennec Fox and Meerkat exhibits are should have been utilised as further space for the Giraffe & Zebra's exhibit, and have visitors see them from the main concreted central path (and can still see the Lions, just in a 'cul-de-sac' and can turn around and head out again down the path), Meerkats and Fenenc Foxes could have very well been exhibited somewhere else in the zoo grounds without too much hassle. Maybe am being too harsh and critical saying, but really agreed with your post.
On a side note, I believe the former Brazilian Tapir exhibit also used to be in this general area too.
I don't believe they've ever been mixed in with the Giraffes permanently. Taronga received a new stallion a few years back and also received the Ostrich last year so this has all likely delayed any plans for introducing the two species. Tbh I don't even know if this is still the plan.I though taronga had mixed there zebras ? unless they have unmixed them. Personally I think they should take a page out of Melbournes book and ditch the zebra and house Nyala with the giraffe. Less issues and would look just as nice.
It's a real shame there isn't a decent viewing spot for both the zebra and ostrich. The exhibit wasn't designed for this section to be sectioned off in the way that it is; as the two main viewing areas overlook the front half which the giraffes have access to.