"Does this article mean we cannot restore the system state if one of those machines fails?"

Not at all.  The article just means that Microsoft changed their stance and that now they only support "only offline system state recoveries are supported for Windows Server 2008  system state recoveries to a new instance of the operating system on the same or  identical hardware"

It says "cannot perform an online restore", can we perform an offline restore and would that make our systems protected?

Yes

Can we use Avamar to protect our Windows 2008 servers

Yes

I've seen the advice to implement WSB for system states, but I wonder if its not something avamar could be fixed for asap?

This is down to a Microsoft support limitation rather than an Avamar specific issue.  More information can be found here:-

Oke , thank you so far for explaining. We still have little discussion here on how to see this.

This offline restore, does it mean, we can deploy a new windows 2008 server and restore an avamar backup of a domain controller without the need for implementing 73 times Windows Server backup?

Lets say a Windows 2008 server is completely lost, can we restore it with Avamar without the need for WSB?

My conclusion is:

In no way we can restore a windows 2008 server without having it backed up with WSB. And WSB is a pain without central administration for 70 servers.

I heard last week that the Avamar v5 SP2 client release is currently undergoing beta testing and provides functionality for Windows Offline System State Recoveries.

Unfortunately I don't have any additional information but if you are interested in participating in the beta programme your EMC sales rep should be able to contact the Avamar product managers to help arrange it.