Every major update in practically every MMO drastically changes the current meta as people adjust to the changes.
And with every major update from every MMO, the response from the community is one of dismay and anger as the classes they spent months researching and perfecting for that current meta have changed.
And you know what usually happens a few weeks after the update? The theorycrafters who design the builds that a vast majority of players use (not everyone enjoys changing builds and running a statistical analysis on dps number...imagine that) come out with a new meta and everyone adjusts. And in a month's time, people are complaining about the game in the same way they were before the update.
Long story short: changes happen with every major mmo update, the community flips out and starts burning their furniture outside ZOS, and then the community adjusts and learns to play the new meta.
For most people, this will be a bump in the road, and for some this is a new opportunity for them to crunch the numbers and find new and innovative ways to be effective. It just depends on the person.
That's not the point. The point is we've tested this on PTS and provided feedback. It has been like this since forever. This patch will get rid of long term players, and while it will probably gain new ones, I doubt they will stay for so long. Many of the theorycrafters you have mentioned have already moved on to a different game. Changes do happen in every MMO, and it is true to ESO too, but this one will kill the game.
Im trying really hard to like this update despire first impression, but everytime i do an activity i get disappointed. As i have not yet figured what to do to avoid sustain problems, i spend most of my time doing heavy attack... i basically dont find it interesting.
Will keep trying for a while to adapt but not sure of the result.