Thanks for clarification, @emilh.
The closest replacement chart to the dual-axis chart is the combined Line and Column widget. You can put count metrics in the line chart and timing metrics in the column below or vice versa.
This chart has to be used on a dashboard. So one possible workaround is to make a dashboard for your metric of interest and then temporarily filter a line and column chart to whichever method or URI you want to view.
Here’s an example of how that could look:
We start with a summary chart. You might use a couple line charts so that you can spot the busiest and slowest methods. Or you might use a table. Or have both.
Below that you have the line and column chart which shows one method at a time. When you find a method in the table or chart above you can open the chart editor and paste the string in to focus on that metric:
Dashboard viewers are able to do this without making any changes to the dashboard itself.
Also once this chart editor is open you can toggle between viewing a table and viewing the line and column chart if you need to keep looking at more methods.
Let me know if this workaround is viable for the customer. If the line and column visualization is working for them we can look into some product enhancements to simplify this workflow.