curse sliggoo isn't that bad and is a p reliable switchinSpecial slig is walled by rose, free spikes. Spdef toge needs to be toxic or psych up to beat serv and again, dogshit vs rose. There are only two defensive pokemon capable of semiconsistently switching into most sets of both ServRose and they are Roselia and Alolan Grimer.
First off you mention that it won't be overcentralizating when you literally mention later in your post that it can beat like 80% of the S and A ranks. And second you are underating the stats of golbat, 75/70/75 is a really good base stats which gives mad bulk, added to this it speed tier allows it to outspeed most of its checks which is amazing and finally it has 80 atk base which is higher than some other mons such as metang, sliggoo or hakamo-o which already hit hard enough.The main reason that I think this mon won't be over powered or over centralizing is that it's raw stats aren't particularly special. It's got good all round stats, decent speed and good bulk with eviolite but that's nothing special in a tier where every mon can run eviolite.
As an NU main i can tell that Golbat isn't used for it's good movepool, is just that its typing is so good as it allows you to have a grass resist, a fighting resist, a ground inmunity and a defog user all in once. The set is always the same 4 moves, 3 if you have another defogger/spinner.The reason it sees use in NU is it's incredible move pool and this, in combination with a great meta typing, is where the bat comes into it's own. Taunt, Defog, Roost, Haze, Super Fang, Whirlwind and Tailwind give it great support options and on the offensive side it's got Brave Bird, Heat Wave, U-turn, nasty plot and even Poison Fang for a toxic that can't be taunted. But a great move pool and good bulk for that move pool don't turn a Pokemon into a superstar or else you'd see a lot more Jigglypuff usage in this meta.
You mentioned 5 mons, that check golbat but idt half of those should be mentioned and i'm going to tell you rn. Kadabra would without any doubts make golbat run all scared but the thing is kadabra can't hard switch in so to get it in front of it, either a double or a u turn/volt switch on the golbat switch or sacking someone would be needed and some of this options may not be the best; even with this kadabra would keep in check golbat definetly thanks to the amazing power creep it has; electabuzz is obviusly a good check to golbat and even that the latter can switch in easier that kadabra on it, you don't want buzz to be slowly chipped since it's usually a key part on volt turns based teams, for the 2 fire mons you mentioned without any speed boost of any kind (scarf or abilities) both would be slower than golbat and would drop to brave bird so if someone should be scared of the other would be the fire types, and lastly you mentioned steel types such as pawniard, but idk if it does make sense to mentions those when you 2 phrases under this say that heat wave is a good move to carry on it.However it's matchups aren't all great. Electabuzz and Kadabra are both extremely common offensive mons with good matchups and while it can switch in on a fighting move from Combusken or Monferno and Brave Bird them, it doesn't want to take a +2 Inferno Overdrive. Steel types also give it trouble if it lacks heat wave, especially Pawniard who can come in on a Defog and do major damage.