The issue with complete randomness in generating a level is that it largely ignores the story based objectives that could be used. As Gangrel mentioned result in combinations that don't adhere to the difficulty range necessary for completion, or end up too easy to complete. Because this is an MMO a lot has to be accounted for from every possible player character build combination to team and multi-team set ups. The work necessary on the back end to create a system that allows for random generation of level maps, the type of faction involved, the possible associated level obstacles that make sense for the faction in question and the location theme of the map that also guarantees that the layout is workable and affords opportunity for multiple play styles would require so much testing that its by far more beneficial to handle level generation in a more feasible manner.

That is create the maps manually, allow for individual spawn placement and random spawn placement (with a rules system that indicates the possible spawn points for different types of spawns and objectives). Many MMOs utilize this type of limited random generation.

With regards to the nemesis idea, it may. It may not be feasible to replicate the exact same system from the Mordor game throughout the entirety of an MMO (or at least the one we are designing at this time) but our lead AI dev has interest in doing something similar for a specific player designated nemesis. It is one of several ideas we have for our nemesis system if we ever implement one (we want to but its a post launch issue to tackle).