Having recently purchased a 480, my experience is the same: little or no ALC. I've made dozens of contacts via PSK and everyone says I have a very clean signal. The 480 appears to just be very PSK friendly.
I you're worried about getting out or how your signal is, pick a time and frequency (10, 15, or 20 meters is where I'm limited right now) and I'll tell you how you're looking.
I am running the exact set-up that you are, Kenwood TS-480SAT with a with a Rigblaster Nomic and I have never experienced the problem you are explaining. Normally I run 50 Watts but often tomes run 75 and even 100 watts without any kind of troubles. I have all of my computer audio settings set to 100% and I use the adjustment knob on the RigBlaster to help adjust for the proper audio out. Any fine tuning I may have to do is done with the mic gain control in order to bring the ALC into proper alignment.
Hope that helps.
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