Returning those territories that were overrun, and controlled by German forces to the rightful governing bodies was just. The reparation amount was absolutely ludicrous. Banning Germany from uniting with Austria was ridiculous. Austria was, and still is, a small country, with German heritage. That would be like saying that Northwest Territories couldnt be part of the United States. Bad example, I know, but along the same lines as far as custom, language, heritage, etc. Limiting Germanys army and navy was simply nothing more than the revenge I mentioned earlier. Russia already had a history of conquest, as well as other European nations which had much to gain by annexing territory traditionally within the bonds of Germany and controlling the financial resources to be had in those acquisitions.
Granted, they were as devastated financially as the rest of Europe, but not having to pay that outrageous reparation would have let Germany recover and become financially sound. As you stated, the depredations of the war in Europe were immense, in lives and in assets. It would have been a coup indeed to see aggression turned against Germany in retaliation. That this wasnt the consideration has no bearing. The possibility existed. The damage the treaty did to the German psyche was of more import than any other consideration. When you lower a group of people, attacking their finances (the treaty caused a widespread and lengthy depression), their national pride and their ability to defend themselves, you leave them ripe for the type of propaganda spewing zealots that take power and commit atrocities. Too harsh? In some respects, yes. A cause of the war? No. A contributing factor, yes.