Do you guys really want Chatot banned? lol
Sure, it's annoying as fuck, but I don't think it's even close to being broken. Offensive teams are full of priority (Refrigerate/Tough Claws Extremespeed, faster Gale Wings), and defensive teams either have little trouble with it, or get haxed. It's incredibly frail, so anything that outspeeds and resists Chatter can simply defeat it if not haxed. Now you might say that that's where the sash comes in, but if using Focus Sash you can't use Substitute, leaving you open to revenge killing by priority and to status. Its Special Attack is also below average, so it can't do much except fishing for hax before a Nasty Plot boost.
I think it can be compared to Shedinja. Shedinja is far from a good pokemon in any meta except Balanced Hackmons, because of its weaknesses to common types, hazards, weather, and pursuit. It's not broken because all good teams automatically have at least one answer to it. It's the same with Chatot. What keeps it from being broken is that all teams automatically have something that can take it on. Now I don't use stall that much in AAA, so I might be wrong about stall always having something that can take it on, but as far as I know, the only way Chatot defeats stall is with an incredible amount of hax.
Yes, Chatot is uncompetitive, as it relies almost completely on luck, which might be reason to at least suspect it; but it honestly should not be and is not used on serious teams.