Distil Networks is more like a CDN (Content Delivery Network), so every traffic to customers website should pass through Distil server. In other words you have to point your DNS to their CDN (that can potentially bring down your site). They keep analyzing your website through out and if the traffic is found malicious they block.

As you asked about competitors, ShieldSquare as a potential alternative, offers following benefits over Distil:
Non-intrusive API integration that will not affect your website performance and uptime.
Zero False Positives that will ensure that your genuine users are never troubled.
I can offer more direction if I know more about your environment.
Best Regards,
Steven

Distil Networks is one of the leaders in this space. They have a good product, although it does add one more layer of complexity to your stack (especially if you already use a CDN). I'd suggest you look at Fastly's offering - they have partnered up with PerimeterX to provide Fastly CDN + Fastly WAF + PerimeterX bot detection all in one package.

I have used CloudFlare for the last year to protect my web site from attacks.

CloudFlare’s technology automatically detects new attacks that arise against any website on its network.

Read more about CloudFlare's security features here: https://www.cloudflare.com/features-security