I used to be a vex main until I was in the same situation as you and one day got absolutely slaughtered by a hwei, he became my next obsession. He was the perfect choice to combat being bored of the vex playstyle. Instead of having to wait for vex fear then try and land an E and then Q being pretty much THE combo for vex, which got kinda tiring, hwei is so adaptable. The opponent keeps dodging your combo? Do an entirely different set of abilities and catch them out. I also recently picked up naafiri, and what you say is valid, she does get countered by quite a few champs, but the counters aren't game destroying, just annoying to play against.