Hey All,
Repeated crashing like this and an update to Diablo III is most likely due to patch looping—which means that the permissions are not set correctly for Diablo III . I’ve posted a few times with solutions that seem to work; so I’ll post the guide again 
However, before you follow the guide for fixing the permissions, I highly recommend NOT allowing Spotlight to index the Diablo 3 folder as it can cause slow downs and possibly crashing as well.
The following are instructions to stop Spotlight from indexing the Diablo 3 folder in macOS Monterey 12.7.6.
1.) While the Finder is active, click the Apple menu at the top left of the screen.
2.) Click System Preferences (System Settings for macOS Ventura and later).
3.) Click Spotlight and then click the “Privacy” tab.
4.) Click the “+” button at the bottom left, and then click on the drop down box at the top and click on your hard drive that contains the Diablo 3 folder (it’s usually called Macintosh HD).
5.) Double click the “Applications” folder to open it within that window and then select the Diablo 3 folder (by clicking on it once). Then click the “Choose” button at the bottom right, and the Diablo 3 folder should be listed as one of the locations that Spotlight will prevent from searching.
The end-objective we want for the above instructions is to prevent Spotlight from indexing the “Diablo 3” folder, which is in the “Applications” folder.
Now, after you have prevented Spotlight from indexing the “Diablo 3” folder, follow the next guide to fix the permissions on the “Diablo 3” and “Battle.net” folders.
As of February 13, 2025 I’m on an M1 iMac running Sequoia 15.3.1 and playing Diablo 3 as native Apple silicon (these instructions should also fix permissions even if you run Diablo 3 in Rosetta).
Try these steps to fix the permissions on the “Diablo III” folder: On a macOS administrator account (I’ve always played Diablo 3 on an administrator account) do the following:
Before the permission steps below, make sure that Diablo III and Battle.net applications are NOT running.
To ensure that Diablo III and Battle.net applications are NOT running, quit both of the applications and then (instructions for macOS Sequoia 15.3.1. Exact instructions may differ on previous operating systems):
1.) While the Finder is active, go to Go menu > Utilities > Open “Activity Monitor” application.
2.) While Activity Monitor is active, click on the “CPU” tab at the top of Activity Monitor’s window. It’s to the left of the “Memory” tab.
3.) While Activity Monitor is active, go to View menu > Columns > select “% CPU” (make sure there is a check mark next to “% CPU”). Then click on “Process Name” sort tab in Activity Monitor’s window to sort processes as descending (alphabetical order starting at top) by “Process Name” (the caret to the right of “Process Name” should be pointing up).
4.) While Activity Monitor is active, go to View menu > select “All Processes”
5.) Then go back into the View menu > select “Filter Processes”
6.) Then type the word “Agent” within the Filter Processes box. A list of all loaded processes will populate that include the word “Agent”.
7.) The process you are looking for has the name “Agent” with the “Battle.net” app icon to its left. Select this process, and ONLY this process, by clicking on it once. Then go to View menu > select “Quit Process”. A window will pop up asking “Are you sure you want to quit this process?”. Click on “Force Quit”.
8.) Repeat steps 5 through 7 if, and ONLY if, “Diablo III” is still open for some reason after quitting it (meaning it is hanging).
9,) Quit Activity Monitor
Then, proceed to fix the permissions on the “Diablo III” and “Battle.net” folders.
1.) While the Finder is active, go to Go menu > Applications > Select the “Diablo III” folder
2.) While the “Diablo III” folder is selected, get info on it by going to the File menu in the Finder > Get Info
3.) With the “Diablo III Info” window active, open Sharing & Permissions drop down (do this only if the Sharing and Permissions drop down is not already open), and click on the lock at the bottom right.
4.) When you click on the lock at the bottom right, a dialogue prompt will come up stating “Finder wants to change permissions on “Diablo III”. Then authenticate with your password and click the “OK” button.
5.) Make sure that all “Names” in the Sharing & Permissions drop down for the “Diablo III” folder has their “Privilege” set to “Read & Write”, then click the drop down button underneath that has 3 dots in a circle and select “Apply to enclosed items…”, another dialogue box comes up asking if you are sure you want to apply this action, then click “OK”. For example: I have three “Names”: my account name, admin, and everyone. The most important “Name” to do this step on is “everyone”. Make sure you “Apply to enclosed items…” even if “Privilege” is already set to “Read & Write”.
6.) Now do the same process on the “Battle.net” folder. While the Finder is active, go to Go Menu > Computer > open the volume where you play Diablo III from, its usually titled Macintosh HD > Users > Shared
7.) Select the “Battle.net” folder in the Shared folder and repeat the process in step 5 above, but for the “Battle.net” folder.
8.) Close all windows in the Finder, then open the “Applications” folder, and open “Battle.net” application.
9.) Do a “Scan and Repair” on Diablo III and WAIT for it to completely finish before you click the “Play” button. Also, whenever Diablo III is updated, WAIT for it to completely update, before clicking the “Play” button. Waiting for completion before playing helps ensure that there isn’t any data corruption with the game files. I have had to reset the permissions like this on the “Diablo III” and “Battle.net” folders after every update to the macOS operating system, and you may have to as well.
10.) Click “Play” to launch the game.
You may not need to follow the next set of instructions, but I’m going to add them anyway to (hopefully) resolve future crashing/lag/slow downs:
1.) Write down or take a screen shot of your current in-game video settings (I took a screen shot before the 2.7.8 PTR for personal reference
)
2.). Set the following in-game video options to these settings:
Display: Windowed (Fullscreen) [I always play in Windowed (Fullscreen), because it allows me to tab out to other apps]
Lock Cursor: Checked
Max Foreground FPS: 60
Max Background FPS: 8
Large Cursor: Checked
Texture Quality: Low
Shadow Quality: Off
Physics: Low
Clutter Density: Off
Anti-Aliasing: None
Low FX: Checked
Then click “Apply” button and click either “Accept” or “OK”, whichever pops up.
Basically, just put all video settings as low, play for a while, then increase video settings as desired to see if it’ll work well.
Hope this helps 
If you have more issues, let me know, I’ll do my best to help out.
EDIT: Added clarity on how to ensure that Diablo III and Battle.net are NOT running.