Raids wipe. They have to, because if every raid group would kill every boss without wiping, the game would be pretty boring. So every raid wipes from time to time, but how these wipes are analyzed differs a lot. Ideally people would discuss in a totally objective manner what caused the wipe, and use constructive criticism to do better on the next try. In the real world analyzing what exactly caused the wipe isn't always easy, so many raids either exercise polite silence, or start bickering in the blame game.
Sometimes there is individual blame. The priest getting caught in Heigan's flames didn't dance fast enough, the rogue catching the dragon's breath obviously stood at the wrong end of it, the off-tank getting Sartharion's fire elemental adds hit by the lava adds should have moved. But often the blame belongs to a whole archetype: tanks couldn't hold aggro, dps didn't do enough damage, or healers didn't heal enough. Unfortunately in most cases this is all connected: The tanks didn't hold aggro because the dps started too early, the dps didn't do enough damage because they died from not being healed, and the healers didn't heal enough because the dps didn't kill the boss fast enough and they ran out of mana.
Although as a healer one objects against being blamed so often, there is a kernel of truth in it: If I had endless mana and a spell that healed the whole raid for 10k health every second, we would wipe a lot less often. Just do the Battle for the Undercity event once, where this is exactly the heal you get, and you see how you just can't die if healed enough. That doesn't mean I accept responsability for every wipe, but in many cases the responsability is shared between the various archetypes.
So it was kind of interesting when we tried Malygos for the first time. We wiped like ten times, and never got past phase 2. But in at least twice of these tries we wiped because we had reached the end of the 10-minute enrage timer with everyone still alive. Which means that even if I had healed much more, the result still would have been the same. For once it was really, and proveable, the dps' fault. :) Not that I think they did anything wrong. Most of us still have several blue armor pieces, some Naxx-10 gear, and very little if any Naxx-25 gear. I'm sure we'll down Malygos when we are better geared. You need both skill *and* gear to kill that one.