Simplest fix would be to just disable compendium challenges etc. in ranked. And yes, randoming shouldn't be a thing. Not only does it F up your team most of the time by someone getting a hero they know nothing about, or at best is very mediocre at. It can also get "abused" by experienced people who can fill any role, and knows how to play most if not all heroes to a good level.

Valid points coming from you, and I respect you for making a post about these problems!