-def +resistance for flower guard/staying alive
-def +ninjutsu for high damage

...Just keep her in the back, and have good tanks/clones.

I still use standard Empress during Matsuri, and I usually go with the following formations. I can provide a text version of them if you prefer. Not sure what you're using at the moment, if you have tried of these I'll see if I can figure something out in arena.

http://i.imgur.com/yw9PMD0.png

http://i.imgur.com/ddJYbel.png

My Karin can take more hits than Kurenai, and Kurenai needs to be alive to heal and shield Hinata or Main. Vs Fire mains I use Hinata's mystery round 1, vs almost anything else I use Karin's. However, this formation does mean your main will be attacked by standards quite quickly if Hinata dies, it's hard to make an Empress formation that does not have this occur, since your main should be move 2 so you can get her mystery off...

http://i.imgur.com/YjtGSZC.png

If you have any other questions feel free to ask. ^^ I'm a little rusty with this build if I'm to be honest. I wish you luck!