she's been kinda outclassed by sheoldred at this point, but if you want to up the legendary theme you could replace debtors' knell with reya dawnbringer. in most decks i'd actually prefer the knell as it's a more resilient permanent type, but unlike knell, karador can recast her. also, you can birthing pod karador into her.
Unless the legendary lands are 100% necessary to your plans I wouldn't bother with Sisay. In the colors and with Karador's reanimation there are so many tutor options that running Sisay for the creatures is sometimes counter productive (you would rather dump some of her targets to yard to bring them to hand in some situations).
I'd almost rather run Survival of the Fittest then Sisay. Or just another creature with different utility (Vorinclex?)