If you haven't watched MobileGamer on YouTube, here's the reason why we don't get a new raid:
GL Kylo can solo HSTR.
A new raid would be even more harder to complete because of the power of these new Galactic Legends. Your toons would just deal less damage there and you could not compete (another reason for the Traya shards as Login reward). It would be very frustrating for a lot of players who don't have their GL Kylo or Ren.
That's why CG decided to skip working on a new raid.