Ichigo's bankai's main power should be speed. He could have rescued Hinamori if he wanted. However, while I've been calling Ichigo a good for nothing idiot in my previous posts, it was made plainly obvious he didn't do anything at all because he was mortally afraid. You could see that by looking at his hands trembling. Only Hinamori getting "killed" snapped him out of his fright.

But I rather call him an idiot because I hate cowards even more than idiots. Also, I'm quite sure he had more chances of finding an opening while the captains were still standing than when they are all cut down... Haha. He was just too chicken to seize any opportunity.

What comes to their bankais, though, unfortunately could be explained by area effects. For example Soi Fon's huge explosion would be useless when they are all so packed together fighting what they thought was Aizen. For all we know, Shunsui's could be the same. Moreover, if they had any suspicion at all they were under the hypnosis, they would need to be even more careful.