NOT a programmer, but could be the huge piles of code that’s accumulated over the years, could be implementation of more and more cross-server stuff, and in the moment when things could very well go wrong, I believe they’ve let go or outsourced more of the stuff like QA and customer service since Microsoft bought Blizzard, not to mention their MO no longer being “it’s done when it’s done” but rather “WE HAVE A DEADLINE! WE PUBLISHED THE ROADMAP! WE MUST HAVE THE PATCH/EXPANSION OUT WHEN WE SAID WE WOULD!!! NO MATTER HOW NOT READY IT IS!!!” And possibly a lot that we know nothing about, probably just stacking up of everything that could go wrong.
STILL, even with shortage of CS reps, in this case, I think those higher-ups should be the ones addressing us. Absolutely no reason for the silence on what is the biggest gathering of affected players (i.e, THIS forum). ZERO excuse for this level of bad customer service and lack of transparency.