Sazh's Chocobo picks up counters like a boss, especially with fetch lands involved
It fits naturally in legend-heavy builds and sees play in Murktide, control, and combo decks that value instant-speed answers without sacrificing land slots
Even more, I do happened to have a healthy number of planeswalkers in the deck, so cheating into play isn't too hard
The deck then adds support through powerful ramp effects, removal spells, anthem effects, etc
Combo players love her because she pairs with synergy-heavy colorless cards like Staff of Domination and Umbral Mantle for infinite mana loops
With the release of top notch delve cards from Tarkir, the delirium mechanic things, flashback stuff, recursive dorks, and even just an increase in good graveyard recursion effects there is a significant increase to the value of self mill