I was thinking about this during some small discussions about the Giant of Babil, and this occurred to me.
One of the biggest interesting "lie" in FF4 is the fact that the Tricker monster (the floating yellow Imp/Goblin) you find in the Lunar Subterrane. It has nothing to do with the fact that it can kick your ass if you cast Lightning on it, but it has more to do with the "floating" aspect.
The property of "floating" for monsters is simply cosmetic. The actual property that causes them to "avoid Quake" is being weak to arrows/projectiles (Air/Wind) so to speak. This is also the ninja reason why the v1 undead version of Milon/Scarmaglione and the Electric Fish are immune to Quake.
So, back to the CPU battle. Those "floating" orbs are actually not immune to Quake. Of course this isn't exactly the most useful info... killing the two smaller orbs (Defender and Attacker) causes the big CPU to own you... twice!
One of the few rare things people have not considered is the reflect property of Float. This technique requires FuSoYa, but it works just as well when Rosa has learned Reflect (if not Float). First off, cast Reflect on any party member (or just put the middle target for simplicity). Then, cast Float on the next turn.
Ideally, you want to give Float status to the Attacker. You have a 1/3 shot of that happening... but it's not necessarily the end of the world if you get it on the Defender. Simply start over if Float status is applied on the CPU... you don't want it immune to Quake. Once you get Float status on either of the orbs, just cast Quake. FuSoYa should be reasonably powerful enough to help out in dealing damage in this battle.. instead of being woefully useless. Rydia's best spell is still Sylph, to counteract the effects of the Attacker's attack... but Titan is still a capable spell in this instance (she's better off with Quake though). Having FuSoYa useful should make it far easier to counteract the healing the Defender does, assuming you gave Float status to the Attacker orb.
Worthy of note from this research.. revived monsters don't retain Float status... which is very different from characters (they still keep the status while in a dungeon).
Hopefully, someone considers this to be a viable option instead of the slow and painful "kill defender and focus on CPU" method or the insane "dish out as much damage after both Attacker and Defender are gone".