Came across the }StatsByRule cube which looks promising and is documented here.
Set RULE_STATS in }CubeProperties to YES before making changes. Find that layout Right to Left seems to be more readable but depends on your rules I guess.
If it does what I hope, you should be able to see the impact of changes to calcs and feeders, not only in terms of timing but dependencies too.
Will be fiddling and will post any useful feedback.