I have to disagree on that point. Back then when I read the first 10 volume without knowing what the author going to do with the big plot, the independent arc really feels like it's really independent and doesn't have anything to do with advancing the plot at all. It feels like the first 10 volume is just like the daily life of Touma facing unfortunate happenings around him, just like any other series early volumes including IS. I still remember back then that the Deep Blood arc and the Angel Fall arc really feels useless to the overall story, and don't let me start with how coincidental the story feels at the crazy nuns arc. There's foreshadowing here and there, but back then I really feels all those arcs was just the opening scene of bigger stories and the character introduced there will only have cameo later in the story. Even so, the author surely proves me wrong by tying all those earlier arc(except the Deep Blood arc) in the later volume.
What makes Index much better with this series IMO is the characterization and the way the author doesn't use any repetitiveness even in the earlier volume. Sure there's some volume where the story development follows a certain formula(Touma get lucky unexpectedly, gets in trouble in the mid-volume, settles everything with his right punch), but even when following the formula, the author always put some spin on the story, especially during the battle, to make it not boring. Compare that with IS where the author just follow the same formula even up to the battle progression(new enemy comes, Ichika and co. get in trouble, Ichika get help for his energy problem, either he becomes a decoy or finishing the enemy with OHKO hit.)
On the other hand, I agree with the biggest failure is in Ichika. Unlike Touma, who's been portrayed as GAR from the start, Ichika was portrayed as a promising amateur since the start. With this kind of setting, the protagonist needs to be developed fast skill-wise or else the story will be ruined because the protagonist become a side character due to his lack of skill, and that's exactly what happened here. The enemy is developing fast skill wise, but the protagonist is still the same stupid amateur with promising potential as he was in the first volume, that's why he ends up as only a decoy in the later volume.
I still have hope that the author can tie all these meaningless arc into something with better overall plot, but he better do it fast or this series will lose one of its reader
. Oh, and I hope Ichika will stop charging head first into battle and use that brain of his for once.
