For some reason, they're going back to the "we need to respect the Horde" approach with Jaina after Battle for Dazar'alor, so she's used for defensive, as of right now.

As for Malfurion, at least for BfA, they are writing him to be on the same level of power as Sylvanas, as their abilities are very much polar opposites. She and Malfurion duked it out many times in the novellas, and pushed each other to stalemates until their last one, when Saurfang intervened. And seeing how Sylvanas likely wouldn't play fair or fight alone if they fought again, nor would Malfurion want to walk into a trap against her, I can't see them going head to head again.