I play a lot of the roster across all the classes, which keeps me in the plat elo, but allows for more variety and fun. When I tighten up my picks I can hover in diamond, but it gets boring and ineffective playing the same three or so heroes, especially with counterpicking and your heroes getting nerfed to uselessness.
How many heroes do you confidently flex to? What’s your philosophy: focus on your very best heroes or mix things up to keep the game interesting. I guess it depends on how often you play. If you only play a few hours a week, then a few heroes is enough.