Then perhaps you should rethink your approach. You seem to come at everything from an incredibly negative position that gives the impression of a deep distaste - at best - for basically everything the game has to offer.
And I guess I just don't understand why you'd continue to play a game where you have such a negative impression of every mechanic and aspect.
I realize this is way off topic, and I don't want to harp on it. I just was hoping to get a better understanding. So let me address the actual topic here:
Suggested builds aren't really intended as a "best build" list, so much as a general guide to what works well. They often fail to include items with the best synergy, which I suspect is intended to encourage players to experiment with builds to find what they like.
Meanwhile, with her rework, Cass doesn't really need Spellvamp to sustain herself. Effective use of her Twin Fang will do the job well enough once you get enough passive stacks.
That said, if you like it and it works for you, that's fantastic! Experimentation and discovery of preferred builds is a huge part of the game, and it's always awesome to find something that works for you.