Teddie's biggest strengths are ice magic and buffs. Chie actually won't learn any more ice spells after Bufula so she becomes pretty much fully a physical attacker after this. Teddie also learns a lot of healing spells, but he's not quite as good as Yukiko in that regard and his SP isn't as high so she's still the best healer.
This is one of my favorite dungeons in the game, the music's great. The boss is pretty tough though, probably the one I had the most trouble with in the entire game. It can use every element, so my suggestion is to max out Yosuke and Chie's Social Links as quickly as possible so that they lose their weaknesses and you have a smaller chance of getting knocked down when fighting the boss. It can use pretty powerful attacks, so if it gets extra turns it can mess you up bad very quickly. Having at least one character with Mediarama is pretty much required for that fight if you want to survive.
