But you can just add multiple DNS providers yourself. I mean you can add the namservers of both easyDNS and cloudflare. EasyDNS just automates this.
In theory they could simply create a few subsidiaries, let's call them saferDNS1,2,3 and have them build completely different redundant DNS architectures, and add then add the resulting nameservers.
That said, it'd be good to see an actual domain that uses this "proactive" feature to see what easyDNS is doing.
I'm not a DNS expert, so... It's not really that simple is it? If you have multiple nameservers I thought they get equal weight, don't they?
So if you have Cloudflare + (ex:) NS1, and you're using Cloudflare for caching, you need your NS1 records to return Cloudflare proxied IPs normally, but origin IPs under failure conditions. That's a lot of infrastructure.
It also fails completely if you're relying on Cloudflare for DDoS protection and IP obfuscation because a failure means your origin IPs get exposed. That's assuming Cloudflare DNS being down means Cloudflare proxying is down too. It might not be the case, but I think you'd have to plan for it.
Then there's also Cloudflare's detection of nameservers. I haven't tried it with more than Cloudflare's nameservers set for a domain, but if your domain doesn't actively use their nameserver they'll drop your site from their system. So, at the very least, you can't use Cloudflare as a secondary DNS provider (at least the last time I checked).
I was talking about just the DNS layer, but ... you can periodically check what IP Cloudflare would return and return that. (There's also the apex-CNAME record type, ALIAS or DNAME, I don't remember right now, but PowerDNS supports it, and you can set up the resolver to use CF's NS.)
Of course CF doesn't support anything like this, but it works well (because they use quasi fixed, static anycasted IPs for the HTTP(S and TCP?) proxying/load-balancing too), even if it's hacky as hell.
If they have any active verification of nameservers, and if they disable the proxies if they detect something bad, then ... it won't work obviously :)
But technically there's nothing amazing in being a registrar of a domain. So both CF and easyDNS are just stubborn in the name of user experience (consistency).
... all in all, working around any SPoF (reliably) will usually require exponentially more resources/engineering/care.
In theory they could simply create a few subsidiaries, let's call them saferDNS1,2,3 and have them build completely different redundant DNS architectures, and add then add the resulting nameservers.
That said, it'd be good to see an actual domain that uses this "proactive" feature to see what easyDNS is doing.