I never actually use Do Once in any of my projects. I’ve never had a need to and I’ve been working with UE on/off since to the 2.0 days and daily since 2016/7.
I tend to fully scope projects down to the individual actors and components. What each needs to do and how/what interactions with other classes there will be (dependencies etc). This helps me prevent gotchas where I have to either refactor a lot or crutch lean on an approach (less work). I think this is my main saving grace.
Overall if a Do Once is helping where Tick chokes it means the executions/logic relying on the variable are too slow. Variable is getting updated too fast to get the desired result.
I’d have to see the code, dependencies, and know exactly what the desired result would be to say anything about usage.