Hi Ewan,
Based on your screenshots, the horizontal scroll bar is not showing in IE 11. Right?
It has reported a lot of incompatibility issue in IE 11. One workaround is change the X-UA-Compatible meta tag. It allows web authors to choose what version of Internet Explorer the page should be rendered as. You can change it like this: <meta http-equiv="X-UA-Compatible"
content="IE=9" />. Please refer to the similar threads below:
ReportViewer scroll issues in IE
ReportViewer 11 with IE 11: report height exceeds limits
Internet Explorer 11 & SSRS ReportViewer
For this issue, I would recommend to submit it to the Microsoft Connect at this link
https://connect.microsoft.com/SQLServer/Feedback. This connect site will serve as a connecting point between you and Microsoft, and ultimately the large community for you and Microsoft to interact
with. Your feedback enables Microsoft to offer the best software and deliver superior services, meanwhile you can learn more about and contribute to the exciting projects on Microsoft Connect.
If you have any question, please feel free to ask.
Best Regards,
Simon Hou