First, I'd like to point out that Yamamoto is probably going to be tricked/trapped again, like he was when he fought Aizen and Wonderweiss. I mean, one simply doesn't attack the most powerful shinigami in Soul Society without being absolutely confident that you can neutralize him.
Secondly, we're probably going to start seeing a higher body count than we saw previously. I mean, this is the final arc, so there's no point in the author preserving the lives of all the fodder characters (which this manga has a lot of). From a story perspective, they brought Ichigo back because he was more powerful than maybe 99% of Soul Society, which means that it's a solid bet most of Soul Society is out-gunned by this new group of opponents.
Thirdly, I don't think it was a kido spell that was used against Ichigo, it looked like another Quincy item. And it did have an effect, it looks like it removed the layer of power provided by his fullbring, the extra pieces on his bankai form.