Need help dealing with repetitive BOT DoS attacks from changing IPs

I need help dealing with repetitive Bot page requests for invalid URLs and common WordPress folders and directories that happen at least 4 or 5 times a day. The bot seems to change their IP Address after 10 or so requests and makes about a 50 requests a second and basically overwhelms my ASP.NET application for a good 15-20 minutes each occurrence..

Like I said i can’t block that IP because it changes every second and 99% of requests are for invalid or abnormal URLs including a Linear-Gradient css value.

Is there a better way to eliminate all these calls and make sure they don’t even get to my web server at all like block them at the IIS level or should i try to redirect the Bot to another URL or application when they initially make a request for such an invalid page rather than trying to process each request