It seems odd that a hacker would target BitShares specifically and leave other coins alone (especially if they have more value). Were any of these other coins bitcoin?
Are you sure it is a hack and perhaps not some bug that made you think your balance is 0? Can you recall exactly what steps you had taken the last time you were using the wallet prior to the next time you unlocked it to find that your funds were gone?
As for security of the client. If your computer was compromised than all of the various coins accessible via that computer are at risk (ignoring any balances that are protected by multisig). Your BitShares balances are protected by keys that are deterministically derived from the wallet master key. That master key is a strong randomly generated key. So, an attacker won't be able to gain access to it simply through a brute force attack even if your password was weak (they would need access to the encrypted master key stored locally to attempt such a brute force attack). The password only encrypts the private keys stored locally in the wallet database on your computer (and the exported JSON wallet backup). But even if you used a really strong password, it still wouldn't protect your funds if the attacker had access to your computer since they could simply run a keylogger to get the password the next time you unlocked the wallet.
All other coins will be operating on the same principle (again excluding multisig protection), so no, BitShares does not have weaker security than other coins.