We did a retry on getting "the Undying" achi done yesterday, after having failed last time due to a minor mistake from one of our paladins. We made it without much hazzle. Actually, in 10man Naxx there aren't many bosses where there is any big risk of dying. Maybe Patch, but no. He is really easy on 10 man. Sapph, KT? Well yeah. If you have too many melee characters on KT that could become a problem. One of our melee, a druid, respecced boomkin to help solve that problem.
It's funny how I have looked upon people named "Uglyman the Undying" and thought "my, that is so cool!", but now that I have it it's just not all that anymore. Because I know how easy it was. In fact, bosses like 4Horsemen were easier when doing them the "achi-way" (splitting the entire raid equally over the bosses) than our usual way. Glory of the Hero was way harder imo.
But I know other people who haven't got the achi yet will look at me now and think "wow, that is so cool!" and that is what it is all for ;)
And the paladin who did the mistake last time wasn't with us this time. He cancelled in the last minute due to lack of sign-ups, but we got a full raid together in the end anyway. Dunno if I should think it divine retribution or feel sorry for him.