Good points all. The Hammerheim re-release in ME3 may have been from an artist they had an individual agreement/contract with, I don't know. The MTGO-exclusive art you referenced (Tabernacle) may be a similar thing. As for Banding, I just recall reading somewhere years ago that WotC had decided Banding was too complex and their user-base didn't like it (personally, I did). But I haven't seen a Banding card since Weatherlight (1997). I am admittedly unfamiliar with the Deadpool set since it's not on MTGO. As for why Hammerheim (and Urborg, for that matter) were in LotR, you got me. I can only think of one creature in the set with land walk (Colossal Whale, Islandwalk), though in that set Mountainwalk and maybe even Swampwalk would have seemed more thematically accurate.
It would be nice (and appreciated) if a Daybreak guru would answer all the above questions for us. Time will tell...