Starcaller
I was never lucky enough to get a shot at Algalon the Observer when we were running Ulduar 25 as progression. The guild I was in at the time experienced quite some drama over Yogg Saron hard-mode attempts to get Val'anyr. Not only were the attempts punctuated by wipes and frustrating, but the priest who was to recieve the mace was the person who made the most mistakes. When ToC was patched in I think that the raid team was relieved to simply move on.
Our 10 man ICC group recently decided to go after Starcaller so that one of our players could match the title to her Celestial Steed. This reason being perfectly reasonable to the rest of us, we all made our way to Ulduar for the evening. One of our number already had the key, so we were able to skip most of the instance and head straight in after amusing ourselves with FL and a hardmode XT. Those tantrums still hurt!
Algalon is still a complex and challenging fight, even for a raid of ICC 10 geared players. The mechanics have really stood the test of future patches quite well, delivering a fight as complicated as almost any in ICC, with one exception - the DPS requirements are now almost laughably low, and as long as we kept most of the raid alive we knew we'd have the damage to down him before the enrage. The real difficulty was going to be in perfecting our execution.
Things we got wrong
Healing
We attempted to two heal the first attempt, and our Paladin healer disconnected almost immediately. The damage going out to the tanks was so high that the second I moved away from the tank to deal with raid damage, they would die. Adding a third healer gave us some breathing room although it did require one of our strongest DPS changing over to her restoration spec.
Portals
A few players stumbled into portals accidentally - including myself. I managed to survive the experience by running around madly healing myself, but the DPS who did the same thing on the next attempt wasn't so lucky. Our OT also managed to step into a portal accidentally - and then, on the way out, step into another again.
Things we got right
Big Bang
Every Big Bang went off without a hitch, with all players apart from the tank phased through a black hole, and with defensive cooldowns or pain suppression on the MT at the appropriate time.
Collapsing Stars
We had assigned our highest ranged DPS to focus on killing the stars, and he almost did too well by killing the first couple almost immediately - but once he started being able to more accurately predict how much damage they would take, killing stars became very smooth with all healers aware raid damage was about to occur.
Living Constellations
We had our Death Knight OT deathgrip the Constellations over black holes to explode them. It was a little hard to tell from my white-knuckled healing tunnel vision, but this seemed to be executed quickly and well.
It's one of the most stressful fights I've ever been involved in, more stressful than any attempts in ICC have been to date. I can honestly admit I was close to tears by the last attempt from the feeling of helplessness as my healing just didn't seem to have enough effect on the raid. I can't speak for the other healers, but I felt more than ever before that I was fighting tooth and nail for the lives of my friends. It reminds me strongly of the complexity of the Yogg Saron fight on 25 - while the mechanics are very different, the sheer quantity of them to keep in mind at once and the high penalty for getting it wrong creates a very similar atmosphere.
Down him we finally did, although I was so far gone in healer tunnel vision I didn't notice the fight was over until the achievement flashed up and the OT flipped off his headphones and started cheering at me. We all gathered in Dalaran for our long-suffering MT to hand in the quest and save all life on Azeroth ... er, again. It's starting to become a bit of a habit, really.
