What happened when you tried random pausing? I use it all the time on a monster app. You said it did not give enough information, and you've suggested you need high resolution. Sometimes people need a little help in understanding how to use it.
What I do, under VS, is configure the stack display so it doesn't show me the function arguments, because that makes the stack display totally unreadable, IMO.
Then I take about 10 samples by hitting "pause" during the time it's making me wait. I use ^A, ^C, and ^V to copy them into notepad, for reference. Then I study each one, to try to figure out what it was in the process of trying to accomplish at that time.
If it was trying to accomplish something on 2 or more samples, and that thing is not strictly necessary, then I've found a live problem, and I know roughly how much fixing it will save.
There are things you don't really need to know, like precise percents are not important, and what goes on inside 3rd-party code is not important, because you can't do anything about those. What you can do something about is the rich set of call-points in code you can modify displayed on each stack sample. That's your happy hunting ground.
Examples of the kinds of things I find:
During startup, it can be about 30 layers deep, in the process of trying to extract internationalized character strings from DLL resources. If the actual strings are examined, it can easily turn out that the strings don't really need to be internationalized, like they are strings the user never actually sees.
During normal usage, some code innocently sets a Modified property in some object. That object comes from a super-class that captures the change and triggers notifications that ripple throughout the entire data structure, manipulating the UI, creating and desroying obects in ways hard to foresee. This can happen a lot - the unexpected consequences of notifications.
Filling in a worksheet row-by-row, cell-by-cell. It turns out if you build the row all at once, from an array of values, it's a lot faster.
P.S. If you're multi-threaded, when you pause it, all threads pause. Take a look at the call stack of each thread. Chances are, only one of them is the real culprit, and the others are idling.