I still have it on 11.10 preview 3 driver (it will be the official 11.10 driver as confirmed by catalystmaker twitter).
I'll have to update then. They may have added it back in. Thanks.
EDIT: Yup. The newer driver version had the option added back in. However, disabling Catalyst AI didn't make any difference in terms of emulation speed so it's not crossfire causing the problem. I'm out of ideas now.