Yesterday and today I went on raids to clear the Ruby Sanctum on ten-man. They were two different raid IDs, but both consisted of guildies and friends, not always on their mains or in their main spec, but nonetheless solid groups. Neither raid got him down, though we got close several times. Still, I felt pretty bad about our failure, especially yesterday as I also happened to be raid leader on that run.
In hindsight I think that I had nobody but myself to blame for that disappointment though, seeing how I made the mistake of reading the European official raids and dungeons forums before the raid, where a thread had already popped up claiming that Ruby Sanctum was oh so easy, people were supposedly one-shotting the boss in pugs etc., which influenced my expectations accordingly. Don't make the mistake of believing everything on the forums!
I'm not claiming that the fight is the hardest thing since heroic Lich King, but it's not nearly the pushover some people make it out to be either. Basically it's not terribly complex, there aren't a lot of different things to watch out for, but situational awareness is key and if you mess up, you're dead.
As a healer, I can never decide whether I love or hate fights with insta-gib mechanics. On the one hand it's nice to not be expected to heal people through their mistakes; they have to learn how to get it right on their own or die. On the other hand... I can't heal people through their mistakes, and if they don't get it right on their own we wipe. Wah! Or at least that's the way it felt on ten-man, maybe twenty-five man is a bit more forgiving about individual player deaths in this particular case (I wouldn't know as I haven't had a chance to try it yet), but on ten even losing one person can quickly mess up the delicate balance between the two realms in phase three and then things tend to spiral out of control.
I also found it noteworthy that Halion seems to be another one of those encounters that are a lot harder on the healers than on anyone else. In tonight's raid I was tanking the boss in the physical realm and it was a pretty damn dull job really. Pull him into position at the start, go through your maximum threat rotation until he goes into phase two, twiddle your thumbs until he returns for phase three, then rinse and repeat what you did at the start. I suppose tanking him in the twilight realm would be a bit more challenging as you have to watch out for the orbs like everyone else, but since you don't have to worry about anything aside from that I reckon that it can't be that much harder.
On Thursday on the other hand I was playing my priest, and healing in the shadow realm was complete madness. Considerable AoE damage going around at all times, constant range issues with some dps, then someone gets the debuff and you have to check whether they are far enough out yet so it's safe to dispel - all this while still keeping an eye on the shadow orbs, and in the meantime the tank gets gibbed by a breath-and-melee-hit combo if he wasn't topped off while the boss got a little stronger in the shadow realm... it's not exactly on the same level as the Lich King fight, but there's still quite a lot to take in at once and I can't blame people for repeatedly messing up on that part in one way or another (including myself). I'm sure it's something that will come to everyone easily enough with some practice, but certainly not after one or two tries, at least not for me and my guildies. Maybe next week.
Oh, and I definitely can't see this boss being very popular with pugs. This isn't a Sartharion, where it doesn't matter if half your raid gets hit by a flame wall. But then I think we've got a bit spoiled in this expansion, expecting a newly released raid boss to go down after a few attempts or even to be puggable in the first week.