I think that some equipment behave differently when used in conjuction with other setups. About 5 weeks ago, I did an Awards gig and was surprised to see and hear the announcer holding the mike almost at waist level and his voice came through loud and clear. At the time the mike in use was a Shure SM58 going through a Behringer compressor limiter then to a Mackie 14 channel mixer.
The SM58 is a cardioid microphone. The Beta 58 is a hypercardiod microphone. The pickup patterns are quite different.
Hyper cardiod microphones have better off axis rejection, but that also means you need better microphone control to use them effectively.
Amature singers and speakers have LOUSY microphone control. That's why you are almost better handing them an omni (except they'll step over in front of the speaker and get lots of feedback).
That lack of off axis rejection SUCKS. I've tried putting pictures of proper microphone placement in my books, but that had mixed results. Half the time they want to hold it out to the side like a rapper, swallow it, or put it at their waist. And a handful want to scream into it (which is why I recommend using microphones that have a high SPL tolerance - and running a compressor/limiter - even if all you use is a hard limit to protect the equipment).It's why you find a lot of karaoke hosts have 'decent' cardiod micrphones on stage, and then have a good cardiod wireless or two they reserve for the better singers who know to ask for them.
And unless I'm mistaken, in the set up you described, the microphone had to be run into the Mackie board, with the compressor/limiter on the inserts. If not, it would have to be run into a pre-amp, then the compressor/limiter, and then the board. Mics normally need to hit a pre-amp before you can process the signal.

