I think Damnation absolutely should be played. Even though it nukes our creatures too, Goyf and Scooze are usually higher quality than your opponent's attempts to rebuild. Hard resets are especially good in the Midrange mirror.
Last Hope is great at cleaning up lingering souls, elementals, etc (things that you really don't want to use Push on, but can't ignore)
And her Ult is absolutely game winning against anything other than decks that ignore the board (combo, Burn, etc) so even if she does nothing but come down t3 against control and + on an empty board, she still needs to be answered. I've played 1 copy in the main of any BGx deck since she was printed
I agree about Ashiok and Nissa though. Nissa is great in Bant but I don't think she's what we want here.
I readily admit to ashiok being a pet card, though the matches it comes in for tend to drag to the point that the slowness is off set. I really do like Last Hope, particularly if the meta calls for it. She has a lot of utility across different matchups, and has no inherent tension with the stubs i run. Main it if your LGS is loaded with aggro, midrange and control, SB it if not, in my opinion.