With regard to QSC products, neither the RMX or the DCA series of amps use a fuse or a circuit breaker. They are designed with protection against full short circuit, open circuit, thermal, ultrasonic and RF interference. They are also stable into reactive or mismatched loads.
@PENG should be able to confirm this.
One of my friends plays instruments in gigs. He has used many amplifier brands over the years, and the only brand of amps that he hasn't killed is the QSC.