Who has the worst support in industry? My vote is for polo.
Yeah, i think polo and yobit probably ties as being first place. Polo might be winning be a small margin though.
Poloniex actually used to have extremely good customer support until like last month, really. Then they started to have deposit and withdrawal trouble, and they removed the trollbox... At least yobit has a trollbox, even though they banhammer you without any reasoning.
being slow to answer is bad but i wouldn't call it "worse support" because at least they answer you at some point and your problem will be fixed eventually.
a worst support in my opinion is when they not only never answer you but also they don't care and they don't fix the problems. and with that definition you have Yobit as your only candidate. 90% of their wallets are dead and they have countless wallets listed. the remaining 10% wallets only have funds in a handful of them such as bitcoin, litecoin, dogecoin and the rest are either empty or fake. good luck getting an answer apart from "it will be fixed soon" out of them
Yobit responds to you if you are someone willing to pay 0.1 BTC to list a pump and dump coin