To the OP, this is a standard "patching practice" used by many MMOs out there, you don't change the game in the middle of a progression season and expect people to not unsub, WoW tried to break these rules during Cata xpac and lost a lot of subs due to it, for half of the xpac, that was the number 1 reason for people to quit the game.

What SE is doing is actually the right thing.

Oh and as for "what type of example this may set" theory, first of all, the problem is not as bad as you are making it out to be (it is bad no-doubt), understand that this is an MMO, things will never be perfect, they have to learn from their mistakes, adjust their balancing philosophy and move on.