Here's another thing. Business plans are an intentional strategy that a company attempts to execute.
While everything you said is correct, it's also pretty well established that this is a recurring event within WotC and by all appearances part of their business plan.
If WotC, as part of the interview process, lays the groundwork and says "most jobs have a duration of X years" you can't say the employees weren't warned. However, unless you're dealing with contract work with a defined term, I've certainly never heard of such a thing occurring.
It may be a fiscally sound strategy by WotC to embark upon these layoffs at regular intervals. It may also be a very shortsighted strategy, i.e. the path of least resistance. I can only speculate.
I have, however, worked in a corporate culture that evolved into a bi-annual layoff cycle. It was incredibly demoralizing, even for those of us who were having success at the company. It became its own form of survivor's guilt and it sucked. However, I'm sure it paled in comparison to those who lost their jobs. Ultimately, I was fortunate enough to find a better job & leave on my terms rather than the company's.
So speculation aside, it goes without saying that for those getting laid off -- it sucks. It may ultimately work out for the better for those people in the long run & it is my sincere hope that it does.
In any event, I hope those who pull this particular trigger within WotC pull their heads out of the backsides and break the trend this year. In the event that they do not, those affected have my sincerest sympathies & well wishes for better & brighter future endeavors.