unfortunately, it's nothing I can fix right now. Part of the issue is, some authentication backends don't support pagination at all, and keystone doesn't support it as well (because of that reason).

This will probably change, when project searchlight is integrated in OpenStack and esp. in Horizon. It is currently under discussion and might see a first solution for mitaka release. It will definitely not being backported.

Radomir - do you think this is something we can do now due to the searchlight integration?

As far as I can see (at https://blueprints.launchpad.net/horizon/+spec/searchlight-instances-integration), there hasn't been much progress with Searchlight integration in Horizon yet. It seems to be a wishlist item for now.

This bugzilla has been removed from the release and needs to be reviewed and Triaged for another Target Release.

Closing as won't fix as searchlight development has stalled.