Rek'Sai, Damage Vs Durability

I love the Kit changes to Rek'Sai, however something feels very off about it. Primarily her ult. The Ult change is great however its damage is horrid. Even when you get someone low it rarely provides enough damage to kill them, which since this is essentially an execution ability doesn't feel right, or satisfying. Perhaps if Riot added in a very brief CC to it, such as a .5 second stun, it is difficult to get off considering the nature of having 5 seconds after last damaging them to actually use the ult. I would love to hear anyone else's thoughts and suggestions.