You guys don't have enough gems. The more gems you have that teach a particular Eidolon = more damage dealt by the Eidolon. For example, Bahamut will do more damage if you have 89 Garnets as opposed to 50.
Storyline=/=gameplay mechanics. You must have whined a lot everytime a character in battle didn't get any fatal wounds/die but s/he did in a cutscene right?
The Invincible is only obtained at the end of Disc 3. So the only goal for the team left is to go to Memoria. And seeing as how it works I doubt it is going to do jack crap against a squadrons of overgrown flying monsters.
'People who have died can not cry anymore, so I cry for them.'-Momo of Shinigami no Ballad Official Leviathan of the Dissidia Board, slithering everywhere.