Once again called back. This time the guy did pick my case up immediately and understood whats happening. He kept me on hold for a few minutes while he contacted whoever.
Supposedly he came back and said my account is lacking certain permissions and such (sounds like the same thing the guy from the first time I called in said) and that he's fixing my account for it now. But in order for them to take proper effect, I have to uninstall ME3 and Origin entirely from my computer, then reinstall them again and it should all work from there.
So I did that. Uninstalled and reinstalled for the 6th time in the last week (an act that is getting real old), and I started up the game again.
Still nothing. Exact same issue happens, won't connect to EA servers, won't authorize the DLC.
This time I had the thought to ask if I should call back if it still doesn't work, he said I should gather dxdiag and msinfo if it doesn't and send it to them so they can work directly from there. So I did that and... then I remembered I'm Australian, and my only options of getting contact with them is phone. Because screw me and my email ability apparently. So APPARENTLY I'll just have to call them back a 5th time...
@holger1405
I asked about the second ME3 in my games list, apparently that should have nothing to do with the issue.
Personally I think he just glossed over it way too fast to even consider it, but what do I know.
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Edit: 5th callback.
Having exhausted every option I've found on these forums, and informing this once again new person on the phone that I've done everything he's asking if I'd done, troubleshooting or otherwise, I've been asked to provide 'dxdiag' and 'msinfo', as well as two 'uotrace' and screenshots of the alerts that come up when I start the game.
He immediately saw in the uotrace that my connection eventually goes to an 'Unknown Host' for five jumps, where the ping suddenly jumps to 230+ms, before it eventually gets to EA. Supposedly it shouldn't be over 100ms, but I don't see that being an issue cause, again, I connect to Mass Effect 2's servers perfectly fine.
Either way, supposedly they're going to have people look at this issue, but they may not be able to come up with anything unless I can contact my internet provider to learn what the Unknown Hosts are and also maybe refresh the ports... or whatever. It was a lot of techno talk I don't understand, and honestly don't think I'd be able to explain to whoever answers the call from my provider.
Really startin' to feel like I'm just not gonna get it and lost the $40 I paid for the bundle.