We don't really have any proof that she's better at healing than anyone in the 4th division. Even if she can...does anyone in Soul Society really know that? Why would they assume so? They certainly weren't there when these hollows were apparently ressurected. All they know is that she's Ichigo's friend, has some healing abilities and is very very silly/dumb. They have a whole division centered on healing...why would they assume they need her?
We have no reason to believe she could have restored Ichigo's powers. Maybe she tried and it didn't work? We don't know if she can heal Bankai's or not. We do know that she's never had any reason to try. Is Ikkaku even aware of her abilities? Why would he go ask a complete stranger to heal his Bankai, when he keeps it a secret from his closest friends?
How do we even know that she's as powerful as you all think she is? Because Aizen said so? Cause he's totally a reliable source of information and has never deceived anyone before?
You guys are just intentionally putting the worst spin possible on every single thing that happens so that you have a reason to complain.