I would find it shortsighted to view Gavilar so definitely this soon and that doing so ignores large chunks of Dalinar's story in Oathbringer and the lessons of that book.
I don't think he wasn't unredeemable while also think his actions as depicted are awful.
If Dalinar can be redeemed and a nderstood in the context of outside influences, depression, addiction etc. we might see something similar for Gavilar.
It also comes down to if a recent and disturbing character change including verbal abuse (unsure if Navami alludes to physical abuse or not...) and it impacting the person permanently as a whole. Are they only made up of a oration of their lives?
It's something we see even in our own world when someone does something out of character but awful.