So the PS4 controller's driver is really weird.
The L2 and R2 triggers read in the range of -1 to +1. Where -1 is depressed. And some inputs overlap.
This is completely different from ALL other controllers out there that read 0 to +1 or 0 to -1. Where 0 is depressed, and absolute(1) is pressed.
This is why your character is spinning when you hold aim, it's registering it as a -1 to +1 input on the rstick which rotates your character.
I've since written a completely new input manager that recognizes PS3 and PS4 controllers and accomodates it. It's going to be in the update that is released later this month.
In the mean time I'd suggest mapping 'AIM' to something like R1 instead of R2. If you give me a moment I'll go grab a PS4 controller and try to come up with a mapping that works and post it here... it's my roommates controller though so I have to wait for him to get home.