To be honest I think this could happen to any provider / hosting environment and although it takes quite long, their only viable option was to block all external access I think..
If you have backups, you could move away from Managed, but they are not the first hoster that has this issue.
If you want to offer your clients more security, you could backup your sites to another hosters network and make sur you can switch to that server when something like this happens. But it also means you need to make sure you have your domain registration / DNS somewhere else. In theory you could do the same for email, but that's also a bit of work, having backup servers for both site and email.
But in my experience, most clients don't want to pay extra for such an insurance, but they do complain / leave if their website is down..