Originally Posted by cyccommute

Don't be fooled by teeth with different profiles. That's not a worn tooth but a design feature. The flatter top on some teeth is going to occur around the lift pin (it that little rivet in your last picture) and they aid in shifting. They make the shifts quicker and smoother.

Originally Posted by cyccommute

Personally, I wouldn't say your derailer is low. It should have 2 to 3 mm of clearance over the teeth. That's about the thickness of a nickel. It doesn't look like you are far from that in your picture.