It’s certainly a reasonable way to get the community’s feel for what’s either overpowered or terrible to play into, however I don’t think there’s enough characters for this to really function properly.
Assuming there’s also some sort of “pick” phase as well as a ban, you’re gonna end up with some characters being uncounterable and favourite characters are gonna be permabanned. Depending on meta, Supports are gonna typically ban Sombra/Genji/Tracer, Tanks will ban Ana/Pharah/Echo/Reaper and Damage will ban whatever counters their favourite character.