User blog comment:Neppudere/The verdict on the LAW/@comment-26843101-20151014220134/@comment-7620285-20151015140521

if you're getting Ace doing a ton of damage (over 30 million?) and still getting Ns, i suspect the loot mechanic is designed to look at your "best attempt" or even average damage per attempt and use the rewards pool based on that instaed of being based on total damage.

the better reward pool many of the strong players are seeing never give Ns (plenty of Rs, because they replaced Ns as the common drop).