Our company relies heavily on burndown charts to track the progress of the different teams. One issue we are facing is that the 'ideal' trend is a straight line that goes from the initial capacity to 0 and that does not represent what the team can do.
If there are days off for example the line should be able to represent that, or if some team members have 'off-topic' tasks not entered in the planning the line should represent that too.
Is there any tool capable of that?
We've found similar issues, and most tools (Jira, TFS etc) do not calculate this.
The simplest solution - go old school and draw it by hand. It takes 5 minutes and there and you have to update manually, but it works well for us.
You can sill use your tool to calculate remaining effort so the hand drawn chart is accurate.
Also, if someone is sick we usually adjust the total effort down by taking something out of the sprint backlog roughly equivalent to what that person would have done on that day. It's not ideal, but at least it normalizes the chart.