Slow file copy performance to DC - but what if we move?

We have a branch office connected to our datacentre with 10 Mbit with only
10% load. All clients are running Windows XP SP2. The DC is Windows 2003 and
all files for our users in on a share on the DC (I know - it's NOT the best
solution).

We have the problem according to the following KB:
321098 - Slow network performance occurs if you copy files to a domain
controller
that is running Windows 2000 or Windows Server 2003
http://support.microsoft.com/default...321098&SD=MSKB

We have noticed since copying a 70 MB file using Explorer to the DC takes 5
minutes. Copying to another server takes less than 2 minutes. We have
doublechecked all server settings (including speed/duplex). The network
itself is not the problem since we have done many other tests using different
tools to check the performance bandwidth - even tried the bandwidth to that
particular server (using other tools than just copying a file with explorer).
I've also tried changing the
HKLM\SYSTEM\CurrentControlSet\Services\tcpip\Param eters\TCPWindowsSize (now
it's set to 64512).

The GPO-settings involved are:
Microsoft network server: Digitally sign communications (always)
Microsoft network server: Digitally sign communications (if client agrees)

But I have a question regarding this: Will this be a problem even if we move
the fileshares to a member server and ENABLE the settings above? Or is it
just a particular problem with DCs?

Is this considered a bug and will be fixed in the future because as far I'm
concerned - I want those settings enabled on ALL servers and ALL clients.