But SE write's the lore, so that could easily be done not to mention be new, shiney and they could get really creative with it from patch to patch. Creating new themes and new forms to the content.

And really if you MUST have single boss fights with absolutely nothing else for the sake of having exclusive content, we already have the primals for that. There is no difference between primals and Alex bosses or coil bosses and that is what I am talking about. They could expand endgame, the zones and the options for what you want to do and what you can do all in a neat package. It would be inclusive to more players and have some really fun tactics. They could be more creative than just throwing bosses in our faces.

And this endgame would still be for a group, its not a one person run thing. It would just give more options in a dungeon then enter here, go here and fight, then fight here, here and here, pop chest and leave.