Best way to retrieve HR assignment end date in a fast formula

Summary:

There is no single DBI that returns an assignment end date. What is the best workaround?

Content (required):

I need to retrieve HR assignment end date in a fast formula for a customer that has multiple assignments. I have seen looping solutions like the one linked below, but this feels inefficient where employees have a lot of assignment changes. I mean it works, but it just feels inefficient.

DBI name for historical Assignment Start and End Dates — Cloud Customer Connect (oracle.com)

Is this really the best way, or would it be more efficient to write some SQL and put it in a value set? To be honest, if that was possible I'd wonder why Oracle hadn't done it to produce a DBI... Is there any reason not to use a value set for this?