True. Whilst the Magic World arc certainly isn't at Bleach-level proportions yet, Akamatsu really needs to move this along, and soon. I mean, so far, every arc has given something to the overall story. The Kyoto arc resulted in Negi gaining leads as to the location of his father, the Demons arc brought about the return of Kotaro and gave Negi significant character development, the Mahorafest arc, on first look, brought us Albireo Imma and his proof that Negi is alive, and on retrospect actually brings us Chao foreshadowing the events of the current arc. And now, the Magic World arc needs to definitively lead us to the next plot development.
However, alexcampos, I think you're exaggerating a little. Whilst we don't know where Nagi is yet, the current arc has revealed two things: 1. He's still alive, as Albireo's pactio proves. 2. He is currently missing because he became a fugitive for rescuing Arika from her execution.
As for Asuna, this arc has shed plenty of light on her, how she was responsible for the events of Ostia, that she is really Arika's cousin, and that she had been travelling with Ala Rubra (although this had previously been hinted at in Asuna's dreams).