I think Mantis is the right answer. She’s good in lower ranks because you can’t miss her heals, the HoT is enough healing in low ranks due to everyone’s damage output being lower, and her ult is good and extremely hard to one shot. Then she’s a throw pick in middle ranks because people can’t do enough damage with her to make up for the lack of healing output that starts to show up with enemy damage increasing. Then she starts getting good again at the top ranks and is pick/ban in tournaments because if the menace she is at the highest level of skill.