I'm gonna jump in and do a little defense here. I played it for about 4 hours yesterday, and honestly, it was a lot of fun. It is not "pay 2 win" that I've run across, but as I understand it, elite versions of dungeons at endgame require keys that are rare drops, or available through payment.
The chapters are made up of one large area, for example, Hell's Kitchen, where it's kind of a free for all, with heroes all over the place. It's more like GW2 where quests will pop up that are area quests that you can chose to particpate in or not, such as a big villain fight, or a defense mission. Within these areas are multiple dungeons, some of which are for the story, some of which are just randomly generated dungeons. These are instanced to the player and their party, or if it is a group dungeon and you are unpartied, it will put you in a group.
The earliest instance of a "world" villain fight was Venom. He just randomly pops up in the docks area, and he spawns SUPER fast. As in less than a minute after he is defeated. It's just a matter of finding him again. They even have villain arrows that pop up to direct you to the world bosses.
I love the crafting system.
If your a Marvel comic and diablo fan, it is awesome. If you are just a diablo fan, it will be good, but not great.
My biggest negative was the pricing structure for unlocking characters and costumes. It's quite expensive if you don't want to rely on them being drops.