I had a similar issue.
They do droop. The issue is the card it too heavy and only supported by two-three tiny screws on back face plate.
One possible solution. Where you have your PCI-E power cables, instead of routing them from the bottom, try routing them from the hole above instead, and pulling them a bit tighter. This should provide support for the otherside and help prevent drooping.
Just make sure the cables aren't pulled too tight.