All Consuming

A few points:

1. This achievement doesn't work the way the description text seems to suggest. Every Consuming Maw you complete for credit will count toward it even if it is the same one all seven times. What is actually happening is that each spawn has a hidden daily quest associated with it that prevents you from getting credit from the same one repeatedly over a short period of time by realm hopping. However, this quest will reset after a day. You know if you can complete the maw again for credit if you go to its location and see a blue arrow on your minimap leading you to it.

2. Sometimes even if you are eligible to complete a Maw for credit, you can be kicked out once inside and the Maw can despawn without giving you a reward. This seems to happen when other players are also inside cleansing it. Don't worry though, you aren't actually locked out. Just wait a few minutes for it to respawn and go back in.

3. These can only spawn in areas that N'Zoth himself is attacking. If you go to the locations in Sipder's list of coordinates while another faction is attacking the area (or none at all), there will never be a Consuming Maw there.

4. They seem to be on spawn timers independent from each other. It's possible for four to be up at once or none. If multiple are up at once, all will give you reputation and credit toward this achievement.

2024 and can confirm you can get this done quickly by logging onto alts. There are no "unique" objectives. Just clear 7 Consuming Maws and you get the achievement.

It seems to be bugged atm.
Completing any Consuming Maw counts towards the achievment, instead of once per unique Maw.