If you just look at the quarters of the four players (and don't look beyond that),
1. I think Roger got a fairly easy draw. Roger should not have trouble (on paper) reaching SF.
2. I think Djoker got the next easiest draw (restricted to just his quarter), among the big three. Dojoker has three easy rounds. In the 4th round he can get Waw / Kandy which could be competitive match. In the QF, he could get Fog / Med (who recently beat Novak) and that too could be competitive.
3. I think Rafa has the toughest draw (restricted to his quarter). He could potentially have a tough match every round (for a change after so many cup cake draws coming his way over the years). In 1R he faces Milkman, who is certainly a tough opponent for the first round. Assuming Kokk is injury free, he is also a tough opponent in 2R (Kokk beat Fed in Miami last year). Although senile and subservient to alpha Spaniard, Verdasco could be a tough opponent on hard courts for Ralph in 3R. In 4R, Ralph could face Isner or Cilic and that could be a tough match also. In QF, Khachanov could give Ralph a run for money (Sasha is the projected QF opponent, but I guess he won't make it there).
But if you focus attention on the last two rounds, obviously
1. Rafa has the easiest draw as he has to face only one other member of 3. Whoever, wins the third quarter
(a lost/next genner) would have already performed beyond their expectations and so would probably
fold to Ralph like a cheap tent.
2. Fed has the second easiest draw. There is some chance that Novak would not make it as Novak's quarter
is tougher than Roger's quarter. Even if both make it, there is reasonable chance that Roger will be fresher
than Novak due to easiness of his quarter.
Whoever wins the top half, most likely will not face Ralph as Ralph's quarter looks tougher than the quarter
of either Novak or Roger. If they face a next / lost genner in the final, obviously they would have the advantage
as the next/lost genner would have already punched beyond their weight.
3. Novak has the toughest draw.
Overall, I am not unhappy with Old Man's draw. Could not ask for much better draw (except for possibly being in Ralph's half).