Not likely. If the sound output is from a card inside the controller then any buzz from the PC wall wart will be isolated to the PC's headphone jack and not present at the controller's output. A PCDI easily resolves the RCAs to a stereo pair of balanced XLRs eliminating any downstream vulnerability.
USB Bus power for a device like this poses no technical issue and it behaves just as any other audio interface including those already built in to the PC (mic and headphone.) There are no other external audio inputs making this device a mere extension of the computer. The whole point of it's design is portability and simplicity. It's Ideal for a bridal shower, but not critical commercial performance.
When the computer crashes, the controller crashes with it. Unlike some units this has no ability to remain functional with external inputs while rebooting or swapping PCs. This is only an issue if live backup is a requirement, and if other audio sources are desired than it is necessary to have an external mixer (which might also eliminate need for the IT.) That;s not an issue at all events. Dead air is not lethal - it's just quiet.
There's no need to EQ a DJ mic. If a DJ doesn't like the sound of his own voice, or it's the wrong type of mic - that's not an EQ issue. Use the talk-over feature or reduce the music while speaking and simply use good audio practice, including changing mics to match the application.
Would I pay $250 for this? No, but I wouldn't criticize any DJ would finds this kind of controller useful for the type of event being described.