As of October 26th, Patch 4.0.1a was released noting that it has corrected this issue. You should no longer need an addon to prevent cogwheels from crashing your client.
HorsemanSummonFix was created to address the current client crashes caused by mousing over specific objects. If you notice additional crashes, feel free to note what is causing them in the comments and I'll add them to the addon.
Thanks to Vladinator for suggesting a solution that works across all clients.
I am no longer receiving crashes while summoning the HHM so I will not know when the issue is fixed. Feel free to leave a comment for other users so they can know when this addon becomes unnecessary.
1.1.7b Rolled back (further) to 1.1.1
1.1.7a Rolled back to 1.1.3
1.1.7 Attempts to display single line tooltips by rebuilding them to prevent crashing
1.1.3 Will now only disable one line tooltips inside of specified zones
1.1.1 Fixed an issue where player location wasn't detected properly because of incorrect map reading