Well, for starters both those cards are much worse than Doom Blade
Artwork has been edited or given alternate art to comply with the governmental standards
Mishra, Eminent Ones ability to copy a noncreature artifact and turn it into a hastey 4/4 Warform creature until the end of turn can be entertaining, especially when targeting cards like Spine of Ish Sah, which bounces back to its owners hand when it leaves the battlefield which you could then replay and kill a thing, or Ichor Wellspring, which can trade as a 4/4 on the battlefield and then draw you a card when it dies
You need to be very cautious or very lucky when choosing who and when to mill or you might make your opponents deck better
A handful of copies of each playtest will gradually enter the market after each MagicFest, to either add to the markets supply or else be absorbed by player demand
Gamma White - Alpha, Beta, Gamma Playtest cards Gamma Blue - Alpha, Beta, Gamma Playtest cards Gamma Black - Alpha, Beta, Gamma Playtest cards Gamma Red - Alpha, Beta, Gamma Playtest cards Gamma Green - Alpha, Beta, Gamma Playtest cards Gamma Gold - Alpha, Beta, Gamma Playtest cards Gamma Artifact - Alpha, Beta, Gamma Playtest cards Gamma Basic Lands - Alpha, Beta, Gamma Playtest cards Others - Alpha, Beta, Gamma Playtest cards MISSING SOURCES (Artifact, Blue, Black) - Alpha, Beta, Gamma Playtest cards MISSING SOURCES (Red, Green, White, Basic Land) - Alpha, Beta, Gamma Playtest cards