Occam's razor - The principle states that the explanation of any
phenomenon should make as few assumptions as possible, eliminating, or "shaving off", those that make no difference in the observable predictions of the explanatory
hypothesis or
theory. This is often paraphrased as
"All things being equal, the simplest solution tends to be the best one."
You shouldn't need the cast of CSI to come here and tell you that since these problems occured immediatly following the update, more than likely there is a correlation there. Is it possible that it's a complete coincidence? Sure it's possible, but not probable. It could have been aliens tampering with your connection, or maybe Nixon's ghost, but the simplest deduction would be that it came as a direct result of the update.
I haven't had these problems yet but i've seen alot of others that have. It is not a dat issue for one. I have seen one day playerA cannot enter Port Jeuno without R0'ing and getting DC. The very next day they can, but then it happens in Ru'Lude Gardens. If it were a dat issue, that would not mysteriously fix itself.
You IT guru's can speculate all you want on what the problem is but that's pretty much all it is is speculation. It's possible that something completely unrelated happened the exact time of the update to cause these problems and is only affecting a random percentage of players, regardless of what system they play on, who their provider is, what geographic region they live in, etc, etc, but is that really likely enough to argue it like a pitbull with a piece of meat?
Argueing that since it's only a small percentage and not the whole doesn't really hold water either btw. Have you ever seen when a car manufacturer orders a recall? Usually it's only something like 5% that have the problems, but it doesn't mean the manufacturer isn't responsible for it. How about if a drug company is coming up with a cure for the cold and the only problem is in their test group 10% of the people on it dropped dead when they took it. Think they'd go, "lolz that's just a coincidence, the FDA will pass us for sure, the other 90% are fine." Reply with apples to oranges all you like, it's the same concept.
Personally i noticed a problem when it took 5-6 hours to download a whopping 90MB patch. I haven't had an update that took more than 20min or so for well over a year. Last time it took so long was back during the whole "ddos attacks" bullshit. You can't say it's just congestion either, it's the same amount of ppl downloading and playing as it usually is. If i was to bet on what the cause, i'd go with what someone else already said, that SE implemented some anti-ddos/hacking/detection programs, and it's screwing with some people's connection. I'll admit that's just an assumption like everything else, but it seems to be the simplest answer.
