Bombardment is actually the best card in the deck, that's the card I'm building around.
HenWen, if seven copies means I'm going to draw multiple "do nothing" cards too often then I should easily grab double-black off ten sources often enough to cast the Muse.
Spider Spawning was in the original build and it was horrible, I thought about keeping a single copy but with no dedicated self-mill it's just too slow.
I knew you'd go Graveborn! Actually I wondered why you didn't still maintain at least 1 copy of SS. It does have potential in this shell for a finisher with both Bombardment and Station (and you've got no other protection for air). The fact that it can flashback and probably gain you 5+ dmg for cast/flashback seems worth the inclusion of just one.
I didn't see Shortcutter coming though. Yes it triggers bombardment and gives you one less blocker the turn it's played but it still seems a bit underwhelming. I thought you might consider
Viscera Dragger since it can still be a '2 drop', can fill the grave for SS, swing big/wide @ haste, be fodder for Station (either hard cast or Unearth) and would be a reasonable blocker if need be (and if you kept Muse, could fuel draw but with Dragger in the midst, that'd be 12 Cantrips therefore Muse is probably not needed).
Based on the recordings you've had so far, I still think some for of spot removal would be fine too (Ground Assault) since you've only got Station to rely on.
Even though Bombardment is a focus of the deck, I think you'd be fine at 3 copies (giving more room for some of these suggestions).
-2 Muse
-4 Shortcutter
-1 Bombardment
+1 SS
+4 Visera Dragger
+2 Assault (3? - you'd have to consider the last cut then if you went all 3 - maybe live without SS but I still think you're selling that option short and this deck could use more 'single card' finishers)
elk