I have a similar problem, the latest iOS OpenVPN client will no longer connect to the Vigor 2862 OpenVpn server, the same error is given in the client's log 'unsafe legacy renegotiation disabled'.
The reason for these errors is the OpenSSL library used in compiling the clients. OpenSSL have decided that legacy renegotiation of keys is a security risk and that enough time has elapsed (the threat has been there for many years) such that this is now disabled by default.
Presumably Draytek (in FW 3 at least, I'm running the latest 3992) are using old OpenSSL libraries and so now all clients using up-to-date OpenSSL libraries will fail to connect (presumably unless compiled with the option to reduce their security level, try getting a 3rd party to do that)!
As an aside, I've read that OpenVPN are no longer supporting compression in v3.4 going forward either, so presumably connections will also fail if the server insists on compression.
In short, unless Draytek will update the firmware and use the modern OpenSSL libraries and a contemporary OpenVPN server config then these devices will no longer work will recent clients.
I'm now forced to install and configure an OpenVPN server on another device on the network, I must admit this has put me off Draytek, I probably won't get another Draytek device unless this issue is addressed fairly quickly. They really should be using libraries that are at least younger than 3 years old and be keeping an eye on developments in server software, it is a network security device after all.
