First off:
Secondly i'm not sure how D2 runs on macs nowadays i used to run it in wine for the first couple of weeks not optimal aswell.
But i made a Bootcamp partition and ran a windows OS on my macbook to play games on you should do this aswell.
you could do this to run the windows version of the game much better.
also blizzard allows you to make free support tickets on this issue!
if you make a ticket explaining the problems you are having while starting the game and they can fix it for you.
it could be implemented to help even more people.
I hope i helped you a bit by this.
and please don't game on your mac.