They have clearly stated in interviews that, in a nutshell:

Alexander (Hard) = Coil Savage

Alexander (normal) = Coil with echo buff

So at this point we all already know what to expect and what the difficulty levels will feel like. If you have run any of the coils with the echo buff on, then you know what normal Alexander will be like. If you have run savage Coil 2, then you know what Hard Alexander will be like, and if you have run any of the coils without echo, than you can expect Hard Alex to be slightly harder than that.