I usually get as far as the tunnel area and then my party dies quickly from the mimics. I am not sure what I am doing wrong. I have it set so every character's (minus Basch of course) second gambit is to heal other characters, is this a mistake?

Anyone have any tips on how to get past this area?

What is your first gambit? Is it [ally:any-->pheonix down] or [foe:attack]? That would make a world of difference.

In general, your gambits should be reviving, healing, attacking. However, with a 4th party member, you could probably stand to have an extra attacker. Also, Basch doesn't do much damage right now (he's unarmed), so you might want to use individual name gambits for healing and not waste your potions/MP on him. Just a suggestion to try.

Check around on gamefaqs.com - there is a 122333 challenge faq that tells you how to get money from a treasure chest, so that you can buy better armor from the Barheim shop.

So should I switch it to "ally: any pheonix down"?

Thanks very much for the advice.

If you have enough LP, buy enough gambit slots so that each of your characters has three gambits. Buy as many phoenix downs and potions from the Barheim merchant as you can afford. Kill monsters and run back and sell the loot if you don't have enough money. (you will probably want to do that to get the merchant's armor, too. You probably won't need more than 30 PDs). Set the first gambit for each character to:
ally:any --> phoenix down

For the 2nd and 3rd gambits, do potion/cure and attack gambits, respectively. Your strongest character (either Vaan or Balthier, I imagine) should attack 2nd and heal 3rd.

Try this strategy and see if it works.

The Mimics are weak to Ice. Set up a Gambit for Fran (and Balthier if he has the License) so that the party leader's target (well mine was Vaan) will be hit with Blizzard.

My Vaan's Gambit was that he'd be healer. Basch can dish out lots of damage too.

just a quick thing, probably a silly question, but the power is still high isnt it?, your not going through and not stopping the battery mimics?, sounds silly i know, but i did it first time only because i want paying attention to balthiers warnings at the start, lol stupid i know, but if you are and your still having trouble, when basch gets his gear near the save crystal, try levelling up near there but let the power drop so you get tougher fiends, then try again.