Glory of the Ulduar Raider (10 player) is an achievement gained by completing all the listed achievements.
Four of the achievements listed in the Meta Achieve have been replaced with easier versions of themselves. While the original achievements still show up in the Glory of the Ulduar Raider (10) Achievement window in-game, if the player clicks on any of the four that have been replaced, they will be brought to the description text for the easier version. See the replacements below:
These mounts are designed similar to the Arena Gladiator mounts as rewards for the top tier of raiders and we will remove the rewards once we have introduced enough new and more powerful equipment to make the completion of these achievements easier than originally intended. Since these rewards are designed for such high-end game play, we currently plan to continue removing any similar rewards we make available in the future.
Glory of the Ulduar Raider Reward Update | 2009-07-22 17:04 |Eyonix
After further discussion, we decided not to remove the [rusted] and [ironbound proto-drake] rewards for the normal and heroic Glory of the Ulduar Raider meta achievements when patch 3.2, Call of the Crusade, launches, and currently have no plans to remove them in the foreseeable future. However, we will continue to evaluate the situation and if a decision is made to remove these rewards at any point in the future, we'll provide a one month warning so players will have time to make some final attempts.