Here's how visitors on Garm has rated every hero in terms of Grand Arena performance. Remember that all tier list-y things should be taken with a grain of salt. If you don't agree with the placements, everything is linked so you can go directly to the hero's page and rate accordingly. And if you want to make sure you're doing your part, here's a page that shows all the heroes you have not rated (must be logged in to use this function).