This latest update is a huge boost to the Sandvich. Although I can't tell exactly how much it heals now, it's way more than 300 HP. I think the real question is whether some classes are even capable of killing him while he's eating.
The ability to drop the sandvich will be a new reason to call people a noob. The same day as the update, I was dying of fire as a medic, and a Heavy casually let me die, even though he had one. After a while, people will figure this stuff out.
In some ways, all this makes Heavy the second best healing class, pulling in front of engie. This is in terms of healing points, not in keeping the team alive.