Blizzard's version of Halloween is up and running, and with it a set of achievements. Well, one of those achievements requires not one but TWO rare-ish drops from the Headless Horseman, a seasonal boss who, like the main event of Brewfest earlier this months, may only be summoned once per player per day. This means that, unless you are a tank or a healer and get invited to additional horseman runs after using your daily summon, you are probably going to have no more than five shots per day at winning a one in five (less if some of your group already has one of the two items) roll on the items.
Via MMO-Champion is a fascinating set of blue posts describing Blizzard's view of how rare these things should be. One point they are clear on is that they are absolutely committed to having this be a random chance, rather than a guaranteed reward (such as a quest, rep, token, etc). That alone is not an entirely popular call - I took a poll on the topic last month, and not one player says that they prefer random loot. Moreover, though they carefully won't reveal the exact numbers (clearly, not knowing the value of the second decimal place on the loot table is all that's stopping Mark Jacobs from swooping in and making Warhammer PVE superior to WoW PVE), they're quite forthright that this means that not all who try will succeed. It's notable because there was another achievement that Blizzard decided in retrospect was too random and removed from the Halloween content, while leaving this one in place, implying that the unacceptable line is somewhere between the two.
So, where is the outrage that I expressed when Blizzard gave Brewfest the same treatment? Well, part of my complaint there was that the Brewfest mount was NOT a random drop in 2007 and became one in 2008, greatly diminishing the value of rest of the holiday. In a broader sense, I don't think it's necessarily a bad thing to have some random achievements that not all players can or should complete. The big issue is when your patch cycle is so slow that the really random stuff is the ONLY thing left in the game for players to do. And, sadly, that particular aspect of the MMORPG industry appears to be par for the course.