Jo'ou: Well, the logic behind Gilder... IIRC, people were failing Aika teams on Floor 3 a lot is my recollection due to SP concerns over whether she could use Delta Shield. Gilder guarantees that she can spam Delta Shield from Floor 3 on.... actually maybe even Floor 2 depending on Moonberries. Will have to look it up. Moreover, shared SP means that they can both actually get to use their damage moves at a relevant pace in fights where blitzing is necessary. I'm surprised more teams don't pair them, actually. If I did replace Gilder, I'd want someone who can ideally status cure Chemist in emergencies (Gilder has Curia) and either has great Physical Defense (Gilder has this) or draining (Orlandu) to survive MT physicals. Not sure I see any good replacements at the 2.0 level - the closest is Kyra, I think?
super: Do agree that the offense level is low, but the hope is that defensively the team holds out - against MT physical damage (the team's biggest problem), Onix still has awesome defense (especially post-Harden), Orlandu can drain, Chemist has Auto-Potion, and that leaves Aika & Gilder to chug Chemist's tossed potions. Gilder can defend if Aura of Denial isn't needed and Aika can heal if Delta Shield isn't necessary. Against ST physical damage, hardened Onix chugging potions. Magic damage eats Delta Shield. Stallers & buffers... well, Gunslinger's nearly a OHKO and hits a huge area that's basically MT, and Orlandu breaks the equipment of PC stallers.
Hmm. Worth working things out somewhat, though. As a random example... take the Floor 4 boss fight, Lufia 2 Erim / Lucia (S3) / Barbariccia (FF4 DS) / Rydia. Rydia & Mage Lucia are getting totally walled, and a Hardened Onix easily shrugs off Barb & Whip Lucia's attacks. Dark Fry is somewhat vexing due to being physical, but Erim just gets blitzed out by Gilder / Orlandu. Flip side, Erim does need to die in two turns, since Dark Fry probably 2HKOs Aika and Chemist ideally is only flipping potions to Onix. And if Onix came into the match Phoenix Downed with 8 HP, there'd be problems. Hrmm.
I did a theme team my first time, I was trying to "win" my second time, figured I'd go back to style for the third. That said, effectiveness is good, and I'm not getting in again for a looong while, so plenty of time to think about options, since the team really does want Onix to never die and that seems the main way it can lose. My kingdom for a Life2 spell...