Sorry to hear about your issue with them but I have to add they are my most trusted exchange for alts, bittrex not that far behind. With poloniex your funds are safe they do seem to have problems with depositing and withdrawing some coins but you know your funds are safe. I notice the first time I had a problem I wrote multiple messages threw frustration and that was the longest they have ever took. It will get sorted soon enough, probably already is?
They might be safer than other exchanges out there but it's a bit of a stretch to say that funds kept with them are guaranteed to be safe. Many exchanges can and have been hacked in the past, and Poloniex isn't immune to this. The only true safe solution to storing funds IMO is keeping your coins locally on your computer (and preferably in cold storage) or in the form of paper wallets.
Exchanges are more or less a necessary evil though. Despite being a generally unsafe place to store your funds, they are necessary for exchanging between coins. By setting up deposits and withdrawals immediately before and after trading and not keeping your coins stored there for any longer than necessary, you can reduce (but not completely eliminate) your exposure to the risk of them getting hacked or running off with your funds (the second one is probably not a huge risk in Poloniex's case but it's definitely a major problem with shadier exchanges).
Not sure where you got me guaranteeing funds being safe. I simply said your funds are safe. You know why? Because mine have for around a year some quite large deposits and withdrawals not a single satoshi lost that is safe enough in this business. If they was hacked which I doubt because they have good security practices then people will be reimbursed.
Who said storing funds on an exchange? No one said storing funds on an exchange but maybe I should have added while trading your funds are safe, saying that though I probably do have a couple of bitcoins worth of alts on there but that is minor a small %, I never risk what I can't afford to lose as everyone should.
As I said I trust them and I would actually trust them with 50% of my holdings if I needed to but luckily that is not needed.