I'm really confused about Rek'Sai

I think has an awesome concept and gameplay, but i'm just so confused about her abilities and how to build her. Before her ult rework i used to play her bruiser/tank, but ever since they changed her ult, her kit makes her feel like she'd work better as an assassin/bursty champion.

All of her scalings only benefit from her bonus AD, so when she's build full-tank, she deals absolutely zero damage. That also means that is pretty much wasted on her, since it would only give her base AD, which none of her abilities scale with.

used to be an interesting pick when she had her attack speed steroid when ranking up her ult, but now she has no atk speed boost, which makes this item lose a lot of it's value.

Without total AD scaling and lack of attack speed steroid, it feels like her options for a bruiser/tanky buld are very limited.

I feel like she might work best as an assassin type of champion. You try to make picks on lonely targets, and in teamfights, you peel and shred whoever tries to engage on your team before trying to make a pick by jumping/ulting a squishy. Like she's somewhat a hybrid between a peel bot and an assassin, since she really can't fully commit to either of these roles.

I just can't seem to find success by playing her tanky, her item options are very limited because of her Bonus AD scalings. Before her rework, it felt like Black Cleaver and sterakk was all i needed for both damage and survivablity. Don't get me wrong though, i really love her new ult, i'm just really confused about how i'm supposed to build her.