Terminal Server secure implementation

Hi all,

I want to install Terminal server in the lan so Users
can log in from home and connect to there pc's.

I need to implement a secure way so I read that TS
will encrypt all the traffic between the client and
server with RCA Rc4 and a key of 128 bit so Its a vpn.
why many companies first installed a vpn client on the
custumers pc to connect to a cisco pix and then after
ther connection is established they open up terminal
client and connect to the terminal server.

I dont see the benefits of encrypting twice the data..
I thing that using just the Ts encryption is enough to
establish a vpn over the internet also changing the
default 3389 port and puting the TS server in the dmz.

Am I wrong?

Thanks,

Juan