We've been using the same job to install MSXML 4 SP3 for years now and have no issues with it working correctly. 4.0 SP3 still installed without error, shows up in programs and features, but the add-on no longer shows up in IE11. Thus, our application doesn't work.
I tried manually install 4, 5, and 6 but none of them will show up in IE11. I'm wondering if the more recent Windows updates broken their own add-on. We've been fretting about crypto locker recently so we pushed all the IE updates would could get to try and stop the exploits. Nothing has been done outside of official MS updates.
Oddly enough, our Windows 8.1 laptops seem to still install it OK.