I've found that most of these insanely complex analytic type queries are easy to model in Core if you treat Core as a DSL and use good programming practice (composition, separation of concerns, etc). The final queries end up being beasts, but if the Core-based pieces are modeled well they are basically equivalent to one I would have written by hand, but with the extraordinary benefit that they can be much more easily parameterized (imagine a financial report where you roll up Year-to-Date, Month-to-Date, Week-to-Date metrics, so using lots of window functions - with the proper structure it's trivial to add a further breakdown allowing you to group by any other metric). I've basically used it to create my own version of Looker.