Let's be clear: nobody left because of new added content. That doesn't make any sense. Adding more content makes game better. No, they left because they 1) were kicked out for cheating (finally), or 2) they can't seem to upset people as much any more (no loot drop), or both.
Add conten is good, change concept is bad if concept is good...it is true it was poor with PVE content before, and now is is more then good, developers do great job in that way and salute that, they put a lot of time to write scripts. On begining of season 3, do you think Khan faction was go to kill other players? Noup we was exploring new content, to see what is everything new... But they hard penalise whole group of people ...PVP players. Many people get caugh chaeting and banned, and they back to this game with proxy servers to play or wait ban expire, or create new character and start from begining... now people don't get some much bans and they not return Heanry, that is fact. If you see complains of some people who don't play and sometime write here post to complain how is game is ruined it is from nostalgy for season 2 what was great game. I dont remember i was play any game so long like season 2 reloaded. I know other players who play for years, and now is gone... Even factions give cancer sometimes on forum, they make even forum more alive... even players in faction wars, they play together, talk each other in game...sometimes bad things was spoken, but sometimes we speak totaly normal each other, make jokes, laugh together etc. I play sometimes here...not like before... waiting and hope i will find something in game was happen, and many people from season 2 who left, I will see them again to play with them or aganst them, to speak with them...