I found that reviving Rosa makes this fight much easier. When the battle starts, use a Phoenix Down with one character and a Hi-Potion with another on Rosa. Rosa should support with White Magic such as Cura, Shell, Protect, etc. If you haven't slowed Golbez, do that with her as well. Cecil should be the Libra caster. Don't waste a precious turn casting Libra with Rosa, as you'll need her to heal. Once you've identified Golbez's weakness, summon the Eidolon with Rydia that deals that damage. I've found that Golbez's weaknesses are usually: Holy, Fire, Ice, or Thunder. I've never seen him with an Earth weakness, so you won't need Titan.
I'm Mountrussmore. No, not Mount Rushmore, Mountrussmore...