Poloniex has major human (and maybe other) resource issues - they lack them. That is the price of having a centralized company which can grow faster then what the owners can handle... happens every day - not just by Poloniex or on the money/crypto market... And that is one reason why I really started to believe in decentralized companies and/or decentralized Exchanges (like Bitshares DEX, etc.)
RE: Steem and SBD deposits still disabaled by Poloniex