Bots are over-fearmongered. Yes, you get a lot of bot traffic to any website. No, it isn't a ddos unless you make it a ddos by making your server do 10 seconds of computation on every page load. Just keep an eye on server load so you know when a solution is actually needed, and you'll be fine. Install Anubis if you want to, but there are even simpler checks, like requiring an image or CSS file to be loaded or setting a cookie or putting a simple redirect in JavaScript or meta-refresh.