I do think the aggro decks have the best synergy thanks to a host of powerful 1-drops in the set, but individual cards feel fair, balanced, and interchangeable
It arrives to the battlefield as a 12/12 with Doubling Season, and then one mana and pull off makes two flying counters, and one mana and pull off gives this two back, so it'll grow by +1/+1 each iteration, and is an infinite combo with any color or no of mana
Use the mana value of the creature as it last existed on the battlefield to determine the value of X
Sage of the Falls starts an infinite combo easily
Then, tap the Clue with Urzas ability for blue mana, tap the Top to draw a card and put it on top of your library, and pay 1 mana to sacrifice the Clue, drawing the Top again