Yeah, Arakko having various Omegas on the Great Ring, the various challengers who haven't actually made it to the Ring, and now Genesis and the two Horsemen that remain with her (War and Famine), there's absolutely no shortage of uber-powerful Arakki who could at least challenge her. We still don't know the extent or limitations of the powers of Isca or Lactuca, other than Genesis herself hesitated to answer Lactuca's offer to fight her personally (and even the Annihilation staff steered her away from accepting that challenge!). "Yeah, you're an Omega plant generator / controller. Fat lot of good that's going to do for you in deep space, beyond Pluto's orbit, where I just teleported you."
And, given the political situation, Ororo doesn't *want* to just fight everyone. She wants to be able to *reason* with them, which adds drama, since she can't just electrocute their brains or whatever to win every argument.