Everyone's favorite weepsack Jaina Proudmoore was an interesting figure in Wrath. She was...all over the place. She had ties to Varian, as the "other" human ruler, and likely his closest peer; she served as mediator between the two factions, stepping in on multiple occasions to prevent an outright outbreak of war; and of course, she had HUGE history with the big guy himself, Arthas.
However, now that Wrath is over and Cataclysm is fast approaching...what is left for her? She's not the face of the humans anymore since Varian is back. She won't be able to be the peacekeeper between the two factions once Thrall steps down as Warchief. And Arthas is dead, leaving her life pretty much directionless.
So what is Jaina supposed to do now? Just sit there in a swamp and watch everyone try to find Tabetha? I guess she could be Varian's advisor but that just makes both characters seem weak. And I REALLY hope they avoid the terrible cliche of her and Varian falling in love just because they are both human rulers. (After all...she hasn't exactly had the best track record with that sort of thing.)
Sure, she's peaceful and happy and could be the conscience of the Alliance, but Velen could do that just as well - better, actually, since being benevolent and caring is pretty much his entire gig. And with the emergence of Dalaran once again, she's no longer even one of the world's last ties to the Kirin Tor, like she was when Dalaran was in its little bubble in Alterac.
At a time when Blizzard is evolving and culling old Vanilla mainstays like Vol'Jin, Cairne, and Mekkatorque, Jaina's outdated and unspecific status in the Alliance hierarchy sticks out like a sore thumb. I think Blizzard missed a great opportunity to send Jaina off with a bang. In my opinion, Jaina's story should have ended in Icecrown Citadel...with her becoming the new Lich King.