Hey yo Blizz!! You got a whole lot of us trapped in a hellish purgatory of Achievement spam. If I went off in chat as many times as this bug goes off, my tiny lil gnome butt would have gotten some sort of warning or maybe even the ban hammer.
Free us from this terrible hell… please… it’s been months and we are all so, so tired 
We gonna keep bumping this post forever.
Major lag when these achievements pop off. Going to be bad when doing a m+ and dying because of it.
Another reply for the cause
Honestly at this point I’d rather them just completely remove guild achievements. Not like they do anything but get in the way with the spamming anyway.
This still occurs even in my alt guild which only has 3 active people (myself and two friends).
It completely lags the game and when in arena it can f you hard
So Since July this has been happening. Cmon Blizzard we know youre a small company with Lots to Do. Remove the Guild Achievements Period.
It’s actually been happening for some guilds since at least 10.2. My guild is one of them.
More achievements seem to have been added to the bug as well, we have Dungeon Diplomat being spammed now with the original 3 the OP mentioned.
Please stop the madness Blizzard!!!
Is this a bug or an unsolvable mystery? Judging by the lack of progress, I’m starting to think you need Sherlock Holmes on your dev team @Blizzard. 
I’d wish you luck fixing it, but at this point… maybe you’ll need more than luck. How about some actual skills? Just saying. 
It’s been happening since the day cross-faction guild support was added, which was 10.2’s launch day 
.
Let’s keep this thread rolling. We the people demand results .
Still a problem Blizz. Please fix.
This problem is so annoying that multiple addons have been created to block guild achievements like GuildAchievementBlocker, GuildAchievementDisabler, SuppressGuildAchievements, DisableGuildAchievements, etc. In my large guild these messages often happen multiple times a minute. Please, blizz, fix this for the sake of our sanity.
Another comment for the cause , we keep this thread alive one comment at a time
Just quit my guild because I keep dying to the lag caused by these notifications!
I stopped playing in the evenings because of this. I’m using the addon and even the slash commands, it stops the popups, but not the lag spikes. Can we get a fix please!
Since July?! And this is happening multiple times a day?!
Come on, man.
As I was posting that message, it happened again.
When this happens while I’m running M+, it makes me want to leave my guild.