Imo Dead Ringer doesn't need to be banned. Its ridiculously situational and the speaker-shattering uncloak noise can be heard from halfway across the map.
My personal philosophy on weapon bans is don't ban just because something isn't used. Only weapons that are abused or annoyingly force a very specific playstyle should warrant whitelisting. If a player can be creative and find a niche for a weapon that is virtually always a direct downgrade, they should be permitted that creative freedom.
Its very easy to spot a feign if you are paying any attention at all, and even if you fail to notice, the spy has like 6 seconds to get out of earshot (again you would have to not be paying any attention at all).
Just some thoughts. Thanks for being so responsive to the community with your development, it really helps a huge amount.
Also: Very unpopular opinion but I think the tide turner should be unbanned. It's a massively high risk high reward weapon. You lose what is without a single doubt the best single weapon BY FAR in the entire game and gain a potential for huge picks and crazy escapes. I dont think anyone will be running the tide turner full time, but it has the potential to spice up an otherwise stagnant demoman metagame.