If they let the current system up and running, then it's between the players to name one, who is allowed to get #1 - #5 (aka "you go for full finish, you go between 80-99% P4, next one 60-79% P4, and so on).
Other guilds, where no on can solo Rancor, they also pick guys, who are allowed to start the Rancor, to make sure, they have the top spot at payout. All others start in P2.
If they change it, what I appreciate, they can either make it random (if several people have the same damage): So it matches the whole game mechanics (RNG)
They can still consider to exclude the 0damage guys, or not.
Another way is, to give the same reward to players, that share the same payout (as in guild dailies).
But this can somehow be abused and there is more work involved in just changing the way, rewards are paid.
This way can be very complex to solve, therefore I would vote for "completely random": You still have the option to solve it your way, by trying to limit damage or work together as a guild.
Btw, I am always #1 if there is a tie. "-3" are the first two digits of my players ID. Even if I do 0damage, I still have the top spot there (#25 to #35), which is always better than others. This is a small imbalance, even if everybody has a small chance of getting a full piece
