I have a player whose character has been using Death Ward constantly. This on it's own is not a problem, but every time he takes a large chunk of damage while at low health, he tries to argue that he's only taking the amount of damage that reduces him to 1, thereby reducing his concentration save on whatever spell he is currently concentrating on.
For example, if he has 11hp, and takes 50 damage, he believes all the damage beyond the first 10 is negated when it stops at 1hp, giving him a concentration DC of 10. Is that right? Or should he still have a concentration DC of 25?