Token doubling effects like Parallel Lives can make this effect even better
It's so perfect I'm surprised it took us this long to get a multicolor anthem
Pillar Analysis: Unique Effect (Creature Tax), Scarcity (Legends, Reserved List), Format Staple (Legacy/Vintage)
My guess is that a lot of Unstable will be sold to players who simply want to experience the novelty of the format once, so they pick up a box to draft with their play group or at their local game store

After taking another look these are cards you'll miss the least IMHO: Rune-scarred Demon (this is a lot of mana for the effect in my experience, and it's better in decks that win via combos), Burning Rune Demon (same as the above, but I like this card a bit more because it's 1 less mana), Patriarch's Bidding (this can be unplayable some games depending on the opponent's deck, and unless I'm missing something you don't have self-mill to make the card better), Kardur Doomscourge (I like this card a lot, but if you need to make space he seems pretty low synergy, also plays poorly with Propaganda effects on an opponent's board), and maybe Rite of Replication (I really love this card, but I feel like it's usually too much mana to 'do the thing', I also feel like you have a decent number of Legendary stuff that can't be copied usefully, I could see this being a pet card)
How do you use Future Sight effects in your decks