I am still playing Dawn of the Dragons, despite the standard social media game mechanics. Something about the energy bars and the false sense of achievement is compelling.
Mission zone 10 is an expansion pack gear reset sort of experience. Players quickly acquire zone 9 gear due to the multiplayer mechanics, and then better from leveling up while wearing it. Along the way, nothing except zone 9 raids do much damage to you. Bosses deal trivial damage, and random encounters deal exactly 1 per attack. And then you hit zone 10.
The random encounters deal more than half my health, even after pumping points into survival. I had never needed consumable items to beat a boss; defeating the first two of zone 10 consumed almost every one I had found in the process of getting there. Wow. Big change.
As an MMO player, you have experienced this many times. The numbers in the new content are an order of magnitude higher than in the old content. In your MMO, this generally blows up the economy as gold costs also increase by orders of magnitude, and a level 1 player can fund his/her first 50 levels by selling a stack of newbie zone crafting materials for what the level-capped players consider a pittance. Here, the zone 9 gear had that same effect by making all the previous equipment irrelevant; they learned from that, and later zones had protections to keep new players from getting twink gear.
Given the sort of game it is, I have two potential interpretations that are in no way mutually exclusive. First, this is the bend in the difficulty curve. Past this point, you will grind, rather than coasting. I am also approaching the bend in the leveling curve. Past that point, you will grind, rather than autoleveling. I do not know what the game looked like at launch, but it would make sense if this were the “base game” ended. Second, cash shop. Past this point, you will spend money, rather than F2P. I cannot say that would be unfair. If LOTRO went F2P by giving away the first 20 levels of content, this game is giving away the first 500 levels of content. It is not LOTRO-quality questing or The Shire, but that is a generous ratio. They even give away cash shop items because you get cash shop currency for leveling up and logging in.
But that is a heck of a wall to hit. And this is on “normal” difficulty in a game that has three higher difficulty levels. I presume the raid bosses from zone 10 are something to do when you have a four-digit level.