I have read the same problems over and over about Poloniex. I have not used them because I do not trade with altcoins but that is a sign that the exchange might have scaling problems of its own. They have broken the record in terms of volume and the more traders use them the more the bugs and glitches appear. It would be a good decision to stay away from them and trade somewhere else.
The same was said of MtGox years ago. There was also Roger Ver who vouched for the exchange and said that it was solvent. A few months later it was it was exposed as illiquid and cannot pay back their customers. I am not saying that Poloniex is insolvent but you should not always believe what they tell you. Keep your Bitcoins in a wallet you control.