Ryan, if you do a search on your hard drive for folders with large amounts of files, more than 100,000, you may find that you have a folder with an unhealthy amount of files in it. It was a while back, but due to a bug in 9.5 flat, a folder that stores some temp files with relation to provisioning (I don't recall the folder, and my test core doesn't have any folders in it with much volume). You probably already have the patch but if you did much provisioning when the bug was present, and have not cleaned up the folder, it is possible that you are having the same issue. If you find a folder like this, you will want to clear it out (make sure you don't have anything in there you want). You may not be able to even go into the folder. You will need to use CMD line to delete everything unwanted in the folder.
Also, if you are not scheduling your templates off of a locked template, you will want to change the way you provision. By design, each time you schedule an unlocked template, it will create a new, locked one. If you instead only schedule locked templates, you will not get new templates created. This makes it much easier to manage the templates and follow the provisioning history as well.
Let me know if this doesn't help any, but it sounds like you have something like this that is preventing you from being able to provision more than a few machines at a time.