This Apache module makes no sense. Let me explain why. I have installed mod_evasive using EasyApache 4 in Cpanel. Then, I have scanned websites on this particular web server using our Sitecozy link scanner. The website returned 403 forbidden and 404 not found errors. We deactivated mod_evasive and it returned to normal. The sitecozy link scanner has been set up to scan 1 page every second to prevent being too harsh with any web server. The crawler uses 25 concurrent connections. It is not like a DDoS attack that would send 100 requests per seconds.
Furthermore, it does not make sense because it seems like this module returns a response. This means that if there is a real DDOS attack the web server will try to return 403 and 404 which will worsen the situation. The web server will get overwhelmed by trying to answer the requests. A web server under attack should drop offending packets. It should not try answering them.
Nothing can replace a good & clever firewall whether it is a hardware firewall or IPTABLES. For your information, when IPTABLES drop packets it does not mean it will mean the client will never get an answer. The client can retry its request and get a response.