People being hacked since the last Server Check.

Assuming a 50 msec delay (which is quite optimistic I think) would make it possible to brute force a 6-symbol password in 582 years, so I have my doubts that this is the approach they're going for here.

I'm going to assume that's taking a character-by-character approach, testing every possible combination (since I don't know the formulas off the top of my head, I have no way of reversing your math to know for sure).
Thing is, that's one of the most inefficient ways to brute-force an account because real humans rarely have passwords such as 4%.sS! but tend to swerve more towards things like c0w123.

Unless we have everyone who has been hacked so far step forward and tell us what their passwords were when they were hacked, we have no way of knowing how complex their passwords were and, by extension, no idea how difficult they would be to brute-force.

My brother's, for example, was absolutely pitiful and I'm quite embarrassed by it.
He just figured his ID and PIC were plenty of security so he didn't take much effort when it came to creating his password.

Based on what I know, the hacker here in Windia who matches these stories seems to do this:
-Run multiple clients.
-Leave everything untradeable, untouched
-Smega "18-1 shopping gogogogogogo", in a similar fashion of the smegas of kMS
-Sells these items really cheap.

If the first thing is true (Which it is), you can't multi client without GameLauncher.

I didn't know multiclient was back at all.

But you could definitely be logged into two different accounts with two different machines.
I do it quite often.