Mouse input should not be compensated for delta time, since it is an absolute value, for how far the mouse was moved during the last tick. At higher fps you’ll automatically get lower values every tick for the same speed of moving the mouse. Controller input on the other hand, should be scaled by delta time, since it’s always in the -1 to 1 range and you want the amount rotated over time to be constant.
This is why sample projects have both a Look (absolute) and a LookRate (scaled by delta time) axis. If you scale the mouse input by delta time you’ll get the effect described in the OP.