Replicated your blueprint code exactly, but couldn’t reproduce the issue 
In your video the Max Once Per Frame property isn’t enabled tho. I’d guess your world delta seconds is already 0.0166 since you inserted that value into the Time pin of the node, but just to make sure could you confirm that you get the same output when you enable it?
Hmmm, I wonder if it’s actually related to your function. Because setting the character’s rotation according to the delta rotation more frequently shouldn’t make it rotate faster with the cursor. And it indeed doesn’t, also tested that just in case. I suspect your function is interfering with something else. In your video we can kinda see how you handle that “camera tilt”, but maybe it’s also present in other parts of your Event Graph. Very interesting 