Casting her and discarding your hand, putting, say, four cards in the graveyard and then drawing five cards, not only gives you enough cards in the grave to get started with Breach, it also gives you fuel in your hand to keep moving
The lack of power is no real issue as the main purpose of the card is to tap for mana which you will find much easier to make use of with lack of colour restrictions
Using the considered best overall cards doesnt always mean they are always the optimal for your deck
Ghalta, Primal Hunger Ive seen this creature be cast as early as turn 3 or 4, and I can imagine some play patterns allow you to cast it even sooner
19 Ria Ivor, Bane Of Bladehold Battle Cry For Phyrexians Suggested Cards: Regal Bunnicorn, Elas il-Kor, Sadistic Pilgrim, Mondrak, Glory Dominus Mite tokens are very easy to flood the battlefield with, and Ria Ivor, Bane Of Bladehold, is one of the ways to accomplish this