Most achievements in world of warcraft are account-wide. It means that you only earn the points once. If you have earned an achievement on one character, you can see it on all your characters. However, you will still see the achievement toast if a second or subsequent character completes the achievement.
Some achievements are "meta achievements." These are achievements that require you to get other specific achievements. For example, "What a Long, Strange Trip It's Been." These achievements generally are account-wide.
A few achievements are account-only. There are two categories of account-only achievements. One is achievements that are not possible to earn on one character. The other categories are achievements that are just brutal to complete on one character, such as 2500 daily quests or 250K honorable kills.
Blizzard has announced that they’ve added account-level changes to achievements earned in Mists of Pandaria. The beta for wow’s next expansion is still running strong, and players will see these changes soon within the game. Blizzard doesn’t want gamers to focus on a single character because of achievements.
There are some stipulations that will stick to these new account-level achievements. Some of them are:
Most achievements are account-wide. It means you only earn the points once. If you have earned an achievement on one character, you can see it on all your characters.
Most criteria aren’t account-wide. It means that if you start an achievement on one character, then you can't finish the achievement on another.
Some achievements will be “meta achievements”. These meta achievements will require you to grab other specific achievements.
Very few achievements are account-only two categories of achievements will be account-only. The first will be achievements that aren’t possible to earn on one toon.
Blizzard has done their best to developing the users’ experience. If you have quite your wow account for some time, maybe it is a good new for you to come back to the game. Choose a high level accounts wow on farmer100 to find more achievements added in the mists of padaria.