No, seriously. It's dreadful.
I've had this conversation in the past with DH; in fact just about every time I need to renew domains. We are not able to renew multiple domains at the same time, and this causes your system to short circuit at times, making the process cumbersome and annoying. (And yes, I am aware of "auto renewal," but this is not an option for me or many customers.)
Every year when I need to renew I get the following error after I go through the steps of renewing my first domain.
Instead of working, I'm waiting until DH's server posts my payment so I can start the process all over again for the next one...and the next one...and the next.
Solution: Put checkboxes next to all of the domains for an account and an option to "renew selected." This would take you to the payment page with the total amount to pay.