Decks that run Young Pyromancer would love to have extra copies for an even greater number of tokens. Saheeli with her passive ability fills that role perfectly, although she is one mana more expensive to cast.
You could also summon a copy of another Young Pyromancer using her minus ability, and effectively have three token generators on the battlefield.
Control decks would be glad to generate tokens as well, since they run a lot of non-creature spells and not enough creatures of their own. In this regard Saheeli may become a great alternative for Lingering Souls in blue-red decks.