One thing I'm curious about as I felt it was one of the most broken parts of 5e is summoning. They implied multiple spirits without binding. now the test is vs x2 force(not sure why they got rid of force for spells and not spirits, though old school force for spells meant less but was significant for spirits) and spirits hit is the drain(I'd of kept it spirits hits x2).
End of the day though without a super focus on it you probably wont be summoning force 9 spirits, but with weapon damage down force 6 is pretty damn durable. Still force 6 will have smaller pools for dodging, attacking, will do less damage, assuming spirits have the same number a initiative dice as 5e they only get one attack. But its pretty tanky for an average of 4 drain, and you could risk a force 9 and its highly unlikely it would kill you or knock you out depending on how they determine if drain is physical or stun.
And a force 9 spirit in this game with attacks doing so much less damage would be unstoppable. If they had done x2 force in dice and x2 hits in drain, you wouldn't risk a force 9 spirit as you easily could be facing 16 drain or something, which to me is how it should be. Even force 6 might hit you for something crazy on a lucky roll, making it a risk. As is even a crazy lucky roll force 6 is mostly fine.
Still my random ass guess given how little we know is overall I think it is probably a nerf, just not as big of one as I think was needed.