Been a year - any update on this issue? Looking for this answer all over and cant find pertinent answers/fixes to this topic.
I posted about this on my blog. The short is, if you’re attaching particles to a skeletal mesh, change tick group of the skeletal mesh. The mistake I made originally was thinking that changing the tick group of my character was the solution, you need to change the tick group of whatever it is that your particles are attached to (i.e. skeletal mesh).
I’m not sure what the current state of this bug is, but for me in UE 4.12.5, this one line of code has fixed the particle lag problem for world-space particle-effects attached to our vehicle skeletal mesh:
VehicleMesh->PrimaryComponentTick.TickGroup = PrimaryActorTick.TickGroup;
Hope that helps.