RDL's killing you could be a clue to other things. Everything kills me, and I just keep doing them until it gets better. Took two years to get the OHS to finally happen. I'm old, so the body has all these defense systems set up already.
Just recently, finally, my body gave up and let me drop into a squat during the snatch. I'll never pull of a Dimas, but I bet I throw farther than he does.
Watching a video of a perfect back squat or discus throw won't get you there. I watch throwers who are about 20 feet better than me, and see what they are doing.
Look up Dan's article on RDL's in GetUp. Sticking that chin out there like you are taking a punch is a clue.