It's going to be a very challenging course. My impression is that the Giro often tries to out-tough the Tour de France. The ToC is usually tougher due to the level of competition and expectations, rather than the actual course itself.
The "cutoff" is usually when the riders actually bother to protest over unnecessary difficulties or a course that's too dangerous, like they did in 2009.
Yes, these guys could do it without doping, they just wouldn't do it as fast and would pick their battles more judiciously on the mountain stages and TT's. The drugs don't reduce the amount of suffering, it just helps them bounce back quicker.