One of the big flaws in the EVA Systems is the issue of the EVA's nervous system connecting and interacting with the nervous system of the pilot. During the manga and the anime, it is shown time and time again that the injuries incurred to the EVA during combat are transferred to the pilot as well, a good example being Zeruel blasting EVA Unit 01's hand off, and Shinji feeling the pain of said action.
Now, this got me thinking, obviously the amount of pain endured would send any normal person in shock, due to multiple factors, like blood loss and outright "pain". If an EVA is seriously damaged during a battle, wouldn't the shock of the "pain and injuries" be enough to kill the pilot?
A very graphic example is Asuka and EVA Unit 02 vs the Mass production Evangelion Units, paying close attention to the sheer amount of damage Unit 02 sustained during the battle, being disemboweled and so on, eventually killing the EVA Unit.