In regards to UE-14819 timer scheduling has some non-trivial overhead, if you’re firing that many timers that often, overhead of scheduling them and managing them can add up. Blueprints, in particular, are problematic because they are still looking up timer handles based on delegate function which is quite expensive. In C++ we’ve pretty much deprecated delegate based APIs and you need to use FTimerHandle APIs to manipulate timers. I plan on reworking blueprint API to also return a timer handle and then supply that handle to other functions, however, there is likely going to be some significant rework required to take advantage of new API as it likely won’t be possible to simply replace existing nodes and have them start using new mechanisms.
I’m hopeful that this will be done in 4.9 timeframe but there are some other higher priority tasks that I have to work through first before I can start in on it.