I did hear from a developer on Linkedin couple months ago. They are pretty aware of all these issues. The difficulty has been transforming Unreal into VFX software, while preserving its efficiency as a game engine first and foremost. Which is understandable.
Their recommendation is to cache as many effects as you can, especially as they continue to roll out the ability to cache physics elements in the engine when it comes to TAA. They are going to continue to update features and fix things like this in time.