I think I'm at this crossroads, too. I experience tingling and numbness in my lower back and legs after going heavy on the deads. This is only for a few minutes after the heaviest of sets, but it still gives me a bit of grief. For example, I have to sit down almost immediately after the set as my midsection/lower back and legs feel like they can't hold me up any longer. It's a mix of that lactic acid burn and ultimate failure feeling where your muscle has nothing left to give. It's not painful, just a numb almost semi-paralysis (although I don't want to be a hypercondriact). I also find I have to occasionally lift my legs, or bend them to reduce the fatigue while I'm sitting down. The feeling's gone after a few minutes, but it feels weird nonetheless and I don't really get this feeling with leg training or anything else for that matter. I don't know if it's simply a case of taking my back to failure or I suffer a similar condition as yourself.
I guess we have to either swap exercises where we can train around the problem (if possible) or simply lower the weight we train with.