As a healer, I found the Thousand Maws of Toto-Rak to be an absolute HELL to try and heal. Whatever wasn't trying to kill your party by beating the crap out of it was trying to kill your party by beating the crap out of it after poisoning everyone. As the healer, you had to be on your toes and know when to use esuna or heal, while keeping yourself alive after ticking off whatever monster was attacking by healing it's victims. While it wasn't really all too hard (not on the level Garuda anyway) it did separate the attentive healers from the idiots who simply chose a healing role so they could get into dungeons faster. I enjoyed every minute of it, and plan to run it again. I hope there are other challenges like this one in later dungeons.