STF is just as good for build planning even for high level builds most of the time.
Let's say I need to test what 34 lvl 24-18 build with greatsword would be like, so I make a lvl 30 version of it: 21-18 STF and try it out keeping in mind that I'd kill enemies a little bit faster and would live a little bit longer when I'm lvl 34. It's all about imagination, mate.