How do you balance dynamic data driven dashboards with design and UX?

I see hundreds of posts and design shots of "dashboards" on things like Dribbble etc - but what lots of them neglect is that they're only ever representing one or two sets of data.

How do you present large data-sets efficiently? I recently ran into this issue when a donut chart would range from having just one data set, or 10 +

Obviously the issue arises here on how best to display the legends, without impacting design and the user experience

Would you group anything representing 20% or below for example as 'Other', what if the user needs to see everything?

I get pie charts/donut charts aren't always ideal for visualising data, but sometimes the client has the final say!