I haven't read the story but Storm sticking up to Scott and refusing his orders certainly isn't a new development.
They even fought over who should lead the team. She has always had a strong leadership/independence streak.
She also hasn't always been "diplomatic/wise". Look at how she dealt with the Morlocks and her fight with Callisto. She made some pretty tough and "undiplomatic" choices. Also, the changes she went through when she met Yuriko in Japan show that her personality isn't simply calm/staid.
You and Black Guardian make fair points. Maybe my current opinion, after being reminded of her free spirited past, is from more recent character development probably from the point that she wed T'Challa. It's just that she always had a likable personality but since Schism she just comes across as less amicable.