We use a popular extension called Headerbid Expert to measure these types of things in most cases. As you can see from the screenshot below, this extension records the response time for each bidder in the auction.
One thing I would add is that the base representation alone can be deceptive. If you click the 'Page Analysis' button in the lower right corner, It will show you not only the bid response time, but also when the requests occurred relative to each other, which I have included below.
This can be especially useful in cases when you are using multiple header partners, and they aren't all in the same standardized wrapper.
Thanks for taking interest and feel free to reach out anytime!