I really enjoyed fighting Nihilus and Sion, but didn't notice much of a difference when fighting Kreia. I was using InSidious's gameplay rework mod at the time, though, so that surely affected some things.
As an idea, what would you think of also upgrading Atris to be a more of a Jedi historian thematic threat? Maybe like a Jedi Guardian/Jedi Master cross class type combo where she has good melee and solid force resistance. She went down so fast that it was extremely underwhelming in comparison with Sion and Nihilus. A simple HP boost with more varied force power usage would be much welcome.
Beyond the scope of this mod, you could also upgrade the Jedi Masters to be more thematic and thereby challenging, but that's a different concept altogether. I just really enjoyed the two aforementioned fights and would love to see something like that with your eye for balance and design. Kavar is solid as a Jedi Guardian/ Weapon Master, but ZeZ could be like a Jedi Sentinel/ Watchmen, with Vrook as a Guardian/Jedi Master with more of a focus on protective powers.
Thanks for the great work!