While assimilate makes nyx immortal and is extremely strong, the absorb ability has fallen behind since all the changes that have been made to it. The drain is massive while the damage buff duration just doesn't last long enough to really take advantage of.
That being said, it would be cool to see these possible changes:
1. The buff to stack up a bit quicker.
2. The buff duration to last a bit longer to actually take advantage of it.
Now the other issue. While it does make her immortal the whole super slow movement speed and unable to use parkour IMO has no reason being a thing anymore. You know, considering we have revenant who is basically immortal with mesmer skin and doesn't have these limitations, nor is it an energy drain so it's extremely energy efficient.
If the augment can't/won't get reworked along with the ability then I propose a new augment mod.
Nyx absorb would no longer be invulnerable and give damage reduction up to 90% while storing status' dealt to her to reflect back on targets with confusion when the ability is deactivated.
Obviously this could be kinda strong but at the same time status' can be stacked so fast already just using weapons so it shouldn't be that big of a deal. Just put a cap on the types or number of stacks that can be applied. It's more of just a primer ability while still retaining the identity of the ability itself in this case, and not needing to fully rework Nyx kit. She's already a great frame if you know how to play her, but the 4th ability just needs some help. Well and her first but we would just subsume that off.