The Sublime Text for Linux is still coded in Gtk2.
I guess that’s a major reason why it doesn’t work well with ibus.
It also wouldn’t work the best in Wayland environment.

Please consider to migrate. Thanks

Obviously Gtk2 would be reason for your issue. I use Ubuntu 14.0 version and I feel the same problem when I access ibus.
I would also request, Sublime to consider migrating to Gtk3 in the near future for better user experience!!