Cybermen Squadron Seven mana is a lot, but Cybermen Squadron is one of the best myriad cards in the game, able to give your artifact creatures myriad
I can see it being used in Prowess mirrors to take out an opposing Stormwing Entity, or as part of an explosive flurry of spells to trigger prowess creatures, return Arclight Phoenix, or perhaps both
Like it was a really cool concept on paper, and they just didnt follow through in the execution
In contrast, you can't cast the adventure side of Bonecrusher Giant with a discover 2, but youd have no trouble with a discover 3
Atalan Jackal definitely feels like a creature that will cross over to a bunch of other decks, using the Skilled Outrider ability to help you ramp when it deals combat damage
While Mill X cards like Wall of Lost Thoughts will churn through four cards for two mana, which isnt a terrible mana to mill ratio, without top deck knowledge theres no way of knowing what exactly youre putting in your graveyard