Need tips: Black Angus striploin

Hello, im rather new to sous vide, and want some tips for my next cook. I have 2 pieces og 1kg Black Angus sirloin.

My plan is:

Bag with salt, pepper, parsely and butter. 55c (medium-rare) for 4~ hours. Sear on very hot pan (i dont have an iron pan). Slice and serve with a balsamen and shallot sauce + sides.

Is there anything i should do to improve?

In my other attempts i've struggled to get a good even sear, and sometimes the taste has been a bit mild/dissapointing. Im not sure if i should use some kind of marinade.