So there are several reasons why I don't think Breena is a good card for this deck:
1. It's not a vampire (doesn't trigger eminence)
2. It's conditional card draw that only triggers once. It doesn't matter how many creatures you attack with, you're only getting 1 card total for the entire attack step. The 2 +1/+1 counters are whatever, barely anything to write home about.
3. Giving our opponents an opportunity to gain value with our own Breena sounds silly and not something we want to encourage, even if they are helping chip away at life totals.
Try reading the Breena again, I think you misunderstood some things
I am much more higher on this card now that I know that you can draw multiple cards with it in a turn. It is definitely worth testing.
1. It's not a vampire (doesn't trigger eminence)
2. It's conditional card draw that only triggers once. It doesn't matter how many creatures you attack with, you're only getting 1 card total for the entire attack step. The 2 +1/+1 counters are whatever, barely anything to write home about.
3. Giving our opponents an opportunity to gain value with our own Breena sounds silly and not something we want to encourage, even if they are helping chip away at life totals.
Try reading the Breena again, I think you misunderstood some things