Recently had my first run in Cutter's Cry, which is what prompted my memory of this thread. Here are 3 tales of healing fails:

My bad:

Queued for Low Level DR, and up pops Cutter's Cry...which I didn't realize I had already unlocked, so I hadn't watched any videos, read any strategy guides, nada. I also had forgotten to repair my gear before the run, and had also completely forgotten that I had recently acquired Regen. Bad news bears.

I told the group I was new, and off we went. I started to get a little worried somewhere in the 2nd or 3rd pull, when my heals weren't restoring as much HP as I'm used to seeing. We hit the first boss, and the wipes began. After about 5 or 6 wipes -- which I'm pretty sure were primarily my fault -- the tank and summoner (bless their hearts) managed to finish it off alone while the other DPS and I were down. We got to the second boss, and someone said it was much easier than the first...which made me feel even worse when I again got repeatedly destroyed, and eventually ran out of mana. By the time we hit the last boss, I felt so horrible that I tried to volunteer to leave & eat the lockout penalty so they could find someone who was less of a moron. Around 5 wipes later, I ate a blue attack and a violet attack in quick succession, and died while trying to keep myself & the other DPS alive. The tank and summoner were again left to themselves, and proceeded to finish the boss while I watched, cheered, and thanked them profusely.

So many jumps into the Shifting Sands, so much running to link back up with the group, so much staring in horror at HP bars draining to zero. Ughhhhhhh. Promptly repaired & upgraded my gear & read about 20 strategy guides. I'll get you next time, you nasty sand cave, you.

Tank's bad:

A few days later, I jumped into Brayflox in DF because it's one of my favorites, and I had never had a bad experience, despite the horror stories I had read on here. On the first pull, the tank never got aggro and I had to resort to popping Medicas to keep the group alive. After round 1, I decided to just skip trying to cure normally, and started to preemptively shoot off a cure II as the 2nd pull started (bad bad bad). While the timer is going, the tank takes 2 hits (one from each monster) and promptly dies. One DPS quits, and the other goes down with me shortly after the tank. Tank thankfully quits after that, and the remaining DPS and I bailed shortly after. Queued up again 15 minutes later & had a perfect trip (I still <3 you Brayflox).

DPS's bad:

Trusty DR pulled up the "More than a Feeler" guildhest. The 2 DPS (who I suspect were new) decided to ignore the advice of the wise NPC dude AND the advice of the tank & myself, and solely targeted the boss while completely ignoring the bubbles. I started to try to DPS as many of the bubbles as possible while healing, but they all started to pop, and it all went to hell in a handbasket. After I went down twice in a spam of Esuna with 10+ poisons stacked on me, I decided to quit -- only time I've ever been the first to bail on a duty. Got the same hest the next day, and it was so easy that the tank said "so booooring" 3/4 of the way through.

Despite the horror stories, I have to say I love healing so far -- dancing the line between exercising restraint and going all-out is really a blast!