The "Path of the Titans" system? Scrapped, and replaced with an overhaul of the Inscription glyph system. Guild talents? Scrapped, with the benefits added automatically instead of allowing guild officers to specialize a given guild. Forcing 25-man progression to be locked together? Scrapped, after a fashion, as a raid lockout can be "split" into ten-person groups and can more easily be swapped. There's a lot of information, but we're not going to attempt to duplicate the excellent coverage of our sister site WoW.com -- instead, those curious should take a look at their roundup post, and the category with links to more in-depth analysis of each announcement.