I am beginning to think you need to tune your laser PSU (as if the PSU is set too low). To do this, you need to know the highest mA draw specification for the laser tube longevity. A guess for an 80w tube may be somewhere in the upper 26 - 28 mA range (but you need to check to be sure).
With this number in mind and with a mA meter on the machine (if you don’t already have an ammeter installled on the machine, they’re a pretty easy retro fit down stream of the laser tube) you can properly tune the laser PSU through the adjustment trim pot.
The cut off floor of your tube should be <= 10%. But this isn’t going to change your results of what you say is over burn (you’re just moving the scale down). You fix that over burn with faster movement, application tape, longer throw lens, air assist, de-focus technique, etc.