Most NFL teams are going to pass on Herzlich. These are the same teams that would pass on a guy with a knee injury, character issues, or if he were undersized. It has nothing to do with cancer. It has to do with risk. Mark's history and the rod in his leg inspire many of us, but to a team in need of help, he represents a player who might get hurt again.
Conversely there will be teams that have already decided to draft Mark if he becomes available in a slot that they deem valuable. They'll view him as a character guy who will learn the system quickly and contribute right away. They are also measuring the risk. Mark may get hurt but no more so than any draft pick. If he gets hurt again or has further complications, they will just wash their hands of like they would with any other late round "flyer" pick.
Mark will be on an NFL roster next fall. We know he won't get the big payday that he might have received pre-cancer, but as this point he just needs one team to give him a shot.