Its a combination of new technology and getting caught with their pants down.
Yes it is 12 years later, but that only made them want/need to pack on the features and create a game far more demanding of its servers than XI could have allowed in the pre-broadband era. Word got out about how much they improved it (again, lots of features) and they got bum rushed by a tidal wave of players.

Dumping the AFK players is bailing with a bucket in an sudden sea of overload.
I'd wager more of it is coming from those of us moving around, killing stuff, and using things like the duty finder.

What they really need is more hardware to deal with all the folks who are hammering away at their new toy.