Ranking dont matter for me as long as I get in top 1000 but shards and wining strike does matter.
So I just do the easist fight all the time. 100% win chance and same shards as the hard battles.

We players get so few copies of the new items that they dont really matters
I got the 2 R-Stayers and the N-slayer so I hope to get all cards.
Bonus should also be added to number of shards players get - that would improve this event a lot.
Atm it is very hard if you only got 1 or 2 slayers.