Half the point of setting TOR when it has been set is because you don't run into the invariable lore that Force Users of any sort (Sith or Jedi) are a rare thing.
Even from a story perspective, the "current" Galactic Empire era where the seminal six episodes take place eventually violated that pillar of the lore, and did so in flagrant magnificence. Sure, weak excuses were made about the Emperor's Hands being not full-fledged Sith and whathaveyou, and a thousand excuses were made about various obscure Jedi that escaped the purge for a whole host of reasons ranging from the believable to the improbable.
When all was said and done, even in that era, a Star Wars Universe where Force Users weren't so rare was a more interesting place, and not less. It's one of the most iconic aspects of the Star Wars universe, and- naturally, a lot of people are going to want to live it.
As for MMOs? If you think anything remains unique for long (no matter how difficult you make it to obtain), you're badly deluding yourself.
And difficulty being it's own reward? Highly subjective. MMO's (good ones, anyway) invariably tend to set the difficulty bar where most players find it rewarding enough, and not just a select few.